WO2009025719A1 - Compositions polymères pour des applications biomédicales et dans le domaine des matériaux - Google Patents

Compositions polymères pour des applications biomédicales et dans le domaine des matériaux Download PDF

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Publication number
WO2009025719A1
WO2009025719A1 PCT/US2008/009253 US2008009253W WO2009025719A1 WO 2009025719 A1 WO2009025719 A1 WO 2009025719A1 US 2008009253 W US2008009253 W US 2008009253W WO 2009025719 A1 WO2009025719 A1 WO 2009025719A1
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Prior art keywords
flexbone
polymer
siloxane
group
bone
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PCT/US2008/009253
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English (en)
Inventor
Jie Song
Jianwe Xu
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University Of Massachusetts Medical School
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Priority to EP08794921A priority Critical patent/EP2178936A4/fr
Publication of WO2009025719A1 publication Critical patent/WO2009025719A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/40—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
    • A61L27/44—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix
    • A61L27/46—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix with phosphorus-containing inorganic fillers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • A61K38/16—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • A61K38/17—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
    • A61K38/18—Growth factors; Growth regulators
    • A61K38/1858—Platelet-derived growth factor [PDGF]
    • A61K38/1866—Vascular endothelial growth factor [VEGF]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • A61K38/16—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • A61K38/17—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
    • A61K38/18—Growth factors; Growth regulators
    • A61K38/1875—Bone morphogenic factor; Osteogenins; Osteogenic factor; Bone-inducing factor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/36—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix
    • A61L27/38—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix containing added animal cells
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/36—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix
    • A61L27/38—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix containing added animal cells
    • A61L27/3804—Materials for grafts or prostheses or for coating grafts or prostheses containing ingredients of undetermined constitution or reaction products thereof, e.g. transplant tissue, natural bone, extracellular matrix containing added animal cells characterised by specific cells or progenitors thereof, e.g. fibroblasts, connective tissue cells, kidney cells
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
    • A61L27/54—Biologically active materials, e.g. therapeutic substances
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
    • A61L27/50—Materials characterised by their function or physical properties, e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
    • A61L27/56—Porous materials, e.g. foams or sponges
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P19/00—Drugs for skeletal disorders
    • A61P19/02—Drugs for skeletal disorders for joint disorders, e.g. arthritis, arthrosis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P19/00—Drugs for skeletal disorders
    • A61P19/08—Drugs for skeletal disorders for bone diseases, e.g. rachitism, Paget's disease
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04—Polysiloxanes
    • C08G77/045—Polysiloxanes containing less than 25 silicon atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04—Polysiloxanes
    • C08G77/38—Polysiloxanes modified by chemical after-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/42—Block-or graft-polymers containing polysiloxane sequences
    • C08G77/445—Block-or graft-polymers containing polysiloxane sequences containing polyester sequences
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K48/00—Medicinal preparations containing genetic material which is inserted into cells of the living body to treat genetic diseases; Gene therapy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
    • A61L2300/20—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices containing or releasing organic materials
    • A61L2300/258—Genetic materials, DNA, RNA, genes, vectors, e.g. plasmids
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L2300/00—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices
    • A61L2300/40—Biologically active materials used in bandages, wound dressings, absorbent pads or medical devices characterised by a specific therapeutic activity or mode of action
    • A61L2300/412—Tissue-regenerating or healing or proliferative agents
    • A61L2300/414—Growth factors
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L2430/00—Materials or treatment for tissue regeneration
    • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants

Definitions

  • the invention relates to composite materials that contain a polymer matrix and aggregates, and in some embodiments, methods of making and methods of using these materials.
  • the materials contain polyhedral silsesquioxanes and/or biodegradable segments.
  • Bone cement such as Plexiglass, polymethylmethacrylate (PMMA)
  • PMMA polymethylmethacrylate
  • Other porous and biodegradable scaffolds are generally not suitable for load bearing applications since they are weak and susceptible to fatigue and fracture.
  • the invention relates to composite materials that contain a polymer matrix and aggregates, and in some embodiments, methods of making and methods of using these materials.
  • the materials contain polyhedral silsesquioxanes and/or biodegradable segments.
  • the invention relates to a siloxane macromer comprising polymer arms comprising a polymer segment comprising: a) monomers comprising hydroxyl groups, b) a reactive group configured to crosslink said siloxane macromer, and c) a connecting group configured to covalently link a biomolecule.
  • said polymer arms comprise a second polymer segment comprising polylactone.
  • said reactive group and connecting group are is selected from the group consisting of hydroxyl, amine, carboxylate, epoxy, azido, methacrylate, methacrylamide, acrylate, acrylamide, alkoxysilane, alkynyl, vinyl, isocyanate, azido, ethynyl, trithiocarbonate, and dithioester groups.
  • the invention relates to a polymer matrix comprising: a) a polymer comprising siloxane macromers, wherein said siloxane macromers comprise polymer arms comprising a polymer segment comprising monomers comprising hydroxyl groups and a connecting group, and b) cross-linkers covalently linking said monomer siloxane macromers.
  • said cross-linkers comprise polyethylene glycol subunits or alkyl.
  • said polymer comprises a biomolecule covalently linked through said connecting group.
  • said biomolecule is selected from the group consisting of a bone mineral binding peptide, an intigrin binding peptide, anionic or cationic motifs that binds oppositely charged second biomolecule, ligand that binds a second biomolecule.
  • said second biomolecule is selected from the group consisting of proteins, growth factors, cytokines, recombinant proteins, and gene vectors.
  • said siloxane is selected from the group consisting of silsesquioxanes and metallasiloxanes. hi further embodiments, said siloxane is a caged structure, hi further embodiments, said siloxane is a polyhedral silsesquioxane.
  • said siloxane is octakis (hydridodimethylsiloxy) octasesquioxane.
  • said siloxane macromer is a siloxane substituted with a polylactone.
  • said siloxane macromer is POSS-(PLA n -co-pHEMA m )i. 8 or POSS-(PLA n ) i -8 wherein n is .3 to 200 and m is 3 to 1000.
  • the invention relates to a composite material comprising the polymer matrix and aggregates distributed within said polymer matrix.
  • said material is biodegradable, hi further embodiments, said aggregates are selected from the group consisting of calcium hydroxyapatite, and carbonated hydroxyapatite, and beta- tricalcium phosphate.
  • the invention relates to a method of making a composite material comprising: i) providing: a) aggregates, b) a siloxane macromer comprising polymer arms comprising a polymer segment comprising: i) monomers comprising hydroxyl groups, ii) a reactive group configured to crosslink said siloxane macromer, and iii) a connecting group configured to covalently link a biomolecule, c) a cross-linker, and d) a solvent; and ii) mixing said calcium phosphate aggregates with said siloxane macromer and cross-linker in said solvent under conditions such that a composite material is formed, hi further embodiments, said siloxane macromer comprises a biomolecule covalently linked through said connecting group, hi further embodiments, said polymer comprises a biomolecule covalently linked through said connecting group, hi further embodiments, said biomolecule is selected from the group consisting of a bone mineral binding peptide, an intigrin binding peptide, anionic
  • said second biomolecule is selected from the group consisting of proteins, growth factors, cytokines, recombinant proteins, and gene vectors.
  • said solvent further comprises a radical initiator.
  • said radical initiator is hydrophilic.
  • said radical initiator is selected form the group consisting of ammonium persulfate and sodium metasulfite.
  • said reactive groups are selected from the group consisting of hydroxyl, amine, carboxylate, epoxy, azido, methacrylate, methacrylamide, acrylate, acrylamide, alkoxysilane, alkynl, vinyl, isocyanate, azido, ethynyl, trithiocarbonate and dithioester groups, hi further embodiments, said cross-linker further comprises ethylene glycol subunits.
  • said solvent is a hydrophilic solvent.
  • more than half of said hydrophilic solvent by volume comprises molecules selected from the group consisting of water, ethylene glycol and polyethylene glycol
  • said siloxane macromer comprises a polyhedral silsesquioxane.
  • said siloxane macromer comprises octakis (hydridodimethylsiloxy) octasesquioxane.
  • said cross-linker is a diisocyanate cross-linker.
  • the invention relates to dental applications such as artificial teeth that comprise composites disclosed herein, hi further embodiments, the invention relates to bone and joint repair applications.
  • said bone is cortical bone or cancellous bone.
  • said bone is a mandible.
  • said bone is located in an animal.
  • said bone is in or near a jaw, joint, hip, shoulder, elbow, pelvis or ankle.
  • the invention relates to a siloxane macromer comprising polymer arms comprising a polymer segment comprising hydroxyl groups and a reactive group configured to crosslink the siloxane macromer.
  • said polymer arms comprise a second polymer segment comprising polylactone.
  • said reactive group is selected from the group consisting of hydroxyl, amine, carboxylate, epoxy, azido, methacrylate, methacrylamide, acrylate, acrylamide, alkoxysilane, alkynyl vinyl, isocyanate, azido, ethynyl, trithiocarbonate, and dithioester groups.
  • said reactive groups are configured to covalently link bioactive molecules.
  • the invention relates to a polymer matrix comprising: a) a polymer comprising monomer siloxane macromers covalently linked, wherein said siloxane macromers comprise polymer arms comprising a polymer segment comprising hydroxyl groups and a connecting group, and b) cross-linkers covalently linking said monomer siloxane macromers through said connecting group.
  • said cross-linkers comprise polyethylene glycol subunits or alkyl.
  • said polymer comprises a biomolecule covalently linked through said connecting group.
  • said biomolecule is selected from the group consisting of a bone mineral binding peptide, an intigrin binding peptide, anionic or cationic motifs that binds oppositely charged second biomolecule.
  • said second biomolecule is selected from the group consisting of proteins, growth factors, cytokines, recombinant proteins, and gene vectors.
  • said siloxane is selected from the group consisting of silsesquioxanes and metallasiloxanes.
  • said siloxane is a caged structure.
  • said siloxane is a polyhedral silsesquioxane.
  • said siloxane is octakis (hydridodimethylsiloxy)octasesquioxane.
  • said siloxane macromer is a siloxane substituted with a polylactone.
  • said siloxane macromer comprises POSS-(PLA n -co-pHEMA m )i-8 or POSS-(PLA n )i-8 wherein n is 3 to 200 and m is 3 to 1000.
  • the invention relates to a composite material comprising the polymer matrix and calcium phosphate aggregates distributed within said polymer matrix. In further embodiments, said material is biodegradable.
  • said calcium phosphate aggregates are selected from the group consisting of calcium hydroxyapatite, and carbonated hydroxyapatite, and beta-tricalcium phosphate.
  • the invention relates to method of making a composite material comprising: i) providing: a) calcium phosphate aggregates, b) a siloxane macromer comprising polymer arms comprising a polymer segment comprising hydroxyl groups and a reactive group, c) a cross-linker, and d) a solvent; and ii) mixing said calcium phosphate aggregates with said siloxane macromer and cross-linker in said solvent under conditions such that a composite material is formed.
  • said cross-linker is a diisocyanate cross-linker.
  • the invention relates to a composite material comprising: a) a polymer matrix comprising a polymer comprising monomers of 2-hydroxyethyl methacrylate subunits, wherein said monomers are linked via a covalent linkage comprising polyethylene glycol subunits; b) calcium phosphate aggregates distributed within said polymer matrix; and c) a peptide.
  • the invention relates to a polymer matrix comprising: a) a polymer comprising monomer subunits comprising hydroxyl groups, wherein said monomers are linked via a covalent linkage, and b) a siloxane covalently attached to said polymer matrix.
  • said siloxane macromer comprises a covalently linked peptide.
  • the invention relates to a composite material comprising: a) a polymer matrix comprising: i) a polymer comprising monomer subunits comprising hydroxyl groups, wherein said monomers are linked via a covalent linkage, and ii) a siloxane covalently attached to said polymer matrix; and b) calcium phosphate aggregates distributed within said polymer matrix.
  • said siloxane is a siloxane macromer.
  • said material is biodegradable.
  • said siloxane macromer is POSS-(PLA n -Co-PHEMAm)I -8 or POSS-(PLA n ) 1-8 wherein n is 3 to 40 and m is 3 to 1000.
  • the invention relates to a polymer matrix comprising: a) a polymer comprising monomer subunits comprising hydroxyl groups, b) cross-linkers, and c) siloxane macromers covalently attached to said polymer matrix.
  • said cross-linkers comprise polyethylene glycol subunits.
  • said siloxane macromers are second cross-linkers.
  • said siloxane macromers comprise covalently attached biomolecules.
  • said biomolecule is a calcium phosphate binding peptide
  • said siloxane is selected from the group consisting of silsesquioxanes and metallasiloxanes.
  • said siloxane is a caged structure, hi further embodiments, said siloxane is a polyhedral silsesquioxane. hi further embodiments, said siloxane is octakis(hydridodhnethylsiloxy)octasesquioxane. hi further embodiments, said siloxane macromer is a siloxane substituted with a polylactone. hi further embodiments, said siloxane macromer is a siloxane substituted with a polylactide.
  • the invention relates to a composite material comprising a polymer matrix disclosed herein and calcium phosphate aggregates distributed within said polymer matrix, hi further embodiments, said material is biodegradable.
  • the invention relates to a material composition made by a) providing, i) a polymer matrix comprising: A) a polymer comprising 2-hydroxyethyl methacrylate subunits, B) a cross-linker comprising polyethylene glycol subunits, C) calcium phosphate aggregates distributed within said polymer matrix; and ii) a biomolecule; b) mixing said polymer matrix and said biomolecule under conditions such that said biomolecule is absorbed to said material, hi further embodiments, said calcium phosphate aggregates are selected from the group consisting of calcium hydroxyapatite and beta-tricalcium phosphate aggregates, hi further embodiments, said calcium phosphate aggregates have a size between 50 nanometers and 50 micrometers, hi further embodiments, said calcium phosphate aggregates are between 30%
  • the invention relates to a composite material comprising: a) a polymer matrix comprising: i) a polymer comprising monomers of 2-hydroxyethyl methacrylate subunits and ii) a cross-linker comprising polyethylene glycol subunits; b) calcium phosphate aggregates distributed within said polymer matrix; and c) a peptide.
  • the invention relates to a method of making a composite material comprising: i) providing: a) calcium phosphate aggregates, b) monomers comprising a first reactive group and a hydroxyl group, c) hydrophilic cross-linkers comprising two or more reactive groups, and d) a hydrophilic solvent; and ii) mixing said calcium phosphate aggregates, monomers and cross-linkers in said solvent under conditions such that a composite material is formed, hi further embodiments, said solution further comprises a radical initiator, hi further embodiments, said radical initiator is hydrophilic. hi further embodiments, said radical initiator is selected from the group consisting of ammonium persulfate and sodium metasulfite.
  • said reactive groups are selected from the group consisting of vinyl, isocyanate, azido, ethynyl, trithiocarbonate and dithioester groups.
  • said first reactive group is a vinyl group
  • said hydrophilic cross-linker comprises polyethylene glycol
  • more than half of said hydrophobic solvent by volume comprises molecules selected from the group consisting of water, ethylene glycol, and polyethylene glycol
  • said hydrophilic cross-linker comprises a polyhedral silsesquioxane.
  • said hydrophilic cross-linker comprises octakis(hydridodimethylsiloxy)octasesquioxane.
  • the invention relates to a method of making a polymer composite comprising: i) providing a cross-linker comprising polyethylene glycol disubstituted with acrylic groups; ii) mixing said cross-linker calcium phosphate aggregates, 2-hydroxyethyl methacrylate, and ethylene glycol under conditions such that a polymer composite is formed; and iii) mixing said composite with a solution comprising a peptide under conditions such that said polymer composite absorbs said peptide.
  • the invention relates to a method of making a polymer composite comprising: a) providing: i) a cross-linker comprising polyethylene glycol disubstituted with acrylic groups, and ii) a biomolecule; b) mixing said cross-linker, biomolecule, calcium phosphate aggregates, 2-hydroxyethyl methacrylate, and ethylene glycol under conditions such that a polymer composite comprising said biomolecule is formed.
  • an elastic composite comprises a polymer with a plurality of hydroxyl groups, preferably poly(2-hydroxyethyl methacrylate) (pHEMA), and calcium phosphate aggregates, preferably hydroxyapatite (HA).
  • composites are formed by crosslinking a polymer with a plurality of hydroxyl groups in the presence of different types of aggregates using aqueous ethylene glycol as a solvent, hi further embodiments, composites are freeze-dried hi order to remove residual water or other solvents, hi further embodiments, composites have mineral-to-organic matrix ratios approximating those of dehydrated human bone, hi further embodiments, composites exhibit fracture resistance.
  • the invention relates to a material comprising: a) a polymer comprising a plurality of monomer subunits comprising hydroxyl groups; and b) aggregates; wherein said material is elastic. In further embodiments, said material is elastic after compressed with a force of between 0.5 and 1 MPa.
  • said material does not fracture under a compression of force between 29 and 100 MPa.
  • said monomer subunits are substituted or unsubstituted hydroxyalkyl acrylate subunits.
  • said monomer subunits are 2-hydroxyethyl methacrylate subunits.
  • said aggregates comprise a hydroxyl.
  • said aggregates comprise calcium salts.
  • said aggregates comprise calcium hydroxyapatite.
  • said aggregates comprise beta-tricalcium phosphate.
  • said aggregates comprise calcium hydroxyapatite of a size between 50 nanometers and 50 micrometers, hi further embodiments, said aggregates are between 30%- 70% by weight of the bulk material.
  • said polymer further comprises ethylene glycol subunits.
  • said material further comprises a component selected from the group consisting of ethylene glycol, polyethylene glycol, and water.
  • said bulk material contains less than 0.5% of water, ethylene glycol, and polyethylene glycol by weight.
  • said material further comprises cells, biomolecules, peptides, saccharides, polysaccharides, or portions thereof.
  • said material is biodegradable.
  • the invention relates to a bulk material comprising: a) a polymer comprising substituted or unsubstituted hydroxyalkyl acrylate subunits and b) calcium phosphate aggregates; wherein said material is between 10%-90% by weight of said calcium phosphate aggregates.
  • said hydroxyalkyl acrylate subunits are 2- hydroxyethyl methacrylate subunits.
  • said calcium phosphate aggregates are calcium hydroxyapatite aggregates, hi further embodiments, said calcium phosphate aggregates are beta-tricalcium phosphate aggregates.
  • the invention relates to an elastic material thicker than 1 millimeter comprising: a) a co-polymer comprising 2-hydroxyethyl methacrylate and ethylene glycol subunits; and b) calcium hydroxyapatite; wherein said material is between 30%-70% by weight of said calcium hydroxyapatite.
  • the invention relates to a method of making a polymer composite comprising: i) providing: a) an aggregate comprising a hydroxyl, b) a first monomer comprising a vinyl group and a hydroxyl, c) a second monomer comprising two vinyl groups and a hydrophilic linking group, and d) a hydrophilic solvent; and ii) mixing said aggregate, first monomer, second monomer, and solvent to form a solution under conditions such that a polymer composite is formed.
  • said solution further comprises a radical initiator.
  • said radical initiator is hydrophilic.
  • said radical initiator is selected form the group consisting of ammonium persulfate and sodium metasulfite.
  • said aggregates comprise calcium.
  • said aggregates comprise beta-tricalcium phosphate.
  • said aggregates comprise calcium hydroxyapatite.
  • said aggregates comprise calcium hydroxyapatite of a size between 50 nanometers and 50 micrometers.
  • said first monomer is a substituted or unsubstituted hydroxyalkyl acrylate.
  • Figure 1 shows EDSs of the cross-sections of as-prepared FlexBone 37% commercial hydroxyapatite (HA) powder (37Com-3-AP) (top) and 37% commercial freeze-dried (FD) FlexBone 37Com-3-FD (bottom).
  • HA hydroxyapatite
  • FD freeze-dried
  • Figure 2A shows compressive force-strain loading curves of FlexBone composites 37Com-3-AP and 37Com-3-FD versus that of the corresponding un-mineralized pHEMA.
  • the compressive stress corresponding to the highest strain (83.7%) reached is labeled next to each curve.
  • Figure 2B shows 37Com-3-AP (top view) and 37Com-3-FD (top and side views) after being released from >80% compressive strains. Arrows indicate the small cracks formed along the edge of the freeze-dried composites upon compression.
  • Figure 3 shows data of compressive behavior of FlexBone as a function of HA content, i.e., compressive loading and unloading force-strain curves of FlexBone samples 48Com-3-FD and 41Com-3-FD, respectively.
  • Figure 4A shows data of structural integration and compressive behavior of FlexBone containing commercial polycrystalline HA vs. calcined HA, i.e., representative compressive loading and unloading force-strain curves of FlexBone 50Com-3-FD (solid curve) versus 50Cal-3-FD (dashed curve).
  • Figure 5 shows data of reversibility of the compressive behavior of as-prepared FlexBone. Repetitive loading and unloading force-strain curves of 40Cal-3-AP and 70Cal-4-AP are at strains less than 40% (up to 1.4 MPa stress) 3 and 5 times, respectively.
  • Figure 6A shows a XRD of a composite prior to cell seeding.
  • Figure 6B shows a XRD of a composite (pre-seeded with 20,000-cells/cm BMSC) 28 days after SC implantation in rat.
  • Figure 7 shows data of size distribution of the calcined HA powders as determined by sedimentation measurements for particles with diameters below 10 ⁇ m. Both the SEM micrograph and the sedimentation measurement plot suggested a bimodal size distribution of the calcined HA powders with most of the particles sized 5 ⁇ m or below and the larger grains over 10 ⁇ m in size.
  • Figure 8 illustrates the synthesis of macromer 2 wherein (i) is 15 eq. allyl alcohol, 6> ⁇ 10 ' 4 eq. Pt(dvs), 20 0 C, Ih, followed by 90 0 C, 1.5 h, N 2 , 90%; (ii) is 40, 80 or 160 eq. rac-lactide, 200 ppm stannous octoate, 115 0 C, N 2 , 20 h, >90%.
  • Figure 1OA illustrates a synthetic route for the attachment of CTA-I to macromer 2 and the subsequent grafting of pHEMA to the macromer CTA by RAFT polymerization.
  • Figure 1OB illustrates a polymer matrix made using a diisocyanate cross-linker.
  • FIG. 1OC illustrates certain embodiments of the invention.
  • FIG. 1OD illustrate certain embodiments of the invention.
  • Polydispersity (M w /M n ) was determined using a PLGeI Mixed-D column on a Varian HPLC equipped with an evaporative light scattering detector.
  • pHEMA poly(2-hydroxyethyl)methacrylate
  • RAFT radical addition fragmentation chain transfer polymerization.
  • FIG. 12 illustrates certain embodiments of the invention.
  • Figure 13 illustrates certain embodiments of the invention where the mineral nucleating peptide is HA-binding peptide (SEQ ID No.: 1) and the cell adhesive ligand is (SEQ ID No.: 2).
  • FIG. 14A illustrates certain embodiments of the invention.
  • FIG. 14B illustrates certain embodiments of the invention.
  • FIG. 15 illustrates certain embodiments of the invention.
  • FIG. 16 illustrates certain embodiments of the invention.
  • FIG. 17 illustrates certain embodiments of the invention.
  • Figure 18 illustrates the synthesis of methacrylamides MA-C3-N3 and GIy-MA.
  • Figure 19 illustrates the functionalization of HA-binding peptide (HA- 12) and integrin binding peptide (GRGDS) with alkynyl and methacrylamido groups for subsequent covalent incorporation with the synthetic graft.
  • Figure 20 illustrates the design of hybrid macromers containing a POSS nanoparticle core, a biodegradable PLA domain), an HA nucleation domain, a negatively charged growth factor retention domain and a cell adhesion domain).
  • the block copolymer segments are sequentially grafted to POSS via ROP and RAFT polymerization.
  • Figure 21 illustrates the structures of macromer CTAs and synthetic routes for the preparation of star-shaped functional macromers. Arrows indicate the fragmentation sites of macromer CTA-I and macromer CTA-2. The stable radicals generated upon fragmentation initiate the subsequent RAFT grafting of functional domains.
  • Route 1 involves sequential RAFT grafting of the functional methacrylamides carrying polar peptide sidechains.
  • Route 2 involves the RAFT grafting of azido-containing methacrylamide, followed by the conjugation of alkyne-terminating peptides to the macromer via the Cu(I)-catalyzed "click" chemistry.
  • Figure 22 illustrates crosslinking macromers via the formation of urethane (A) and triazole (B) linkages.
  • Cross-linkers PEG-diisocyanate and PEG-dialkyne are both synthesized from commercially available PEG.
  • Crosslinking density in both cases can be varied, with the stoichiometric ratio of 1, 2 and 4 equivalents of cross-linker per polymer arm (or 8, 16 and 32 equivalents cross-linker per macromer) applied.
  • Figure 23 illustrates polarized light micrographs of H&E and ALP/TRAP stained FlexBone explants (50% HA, without exogenous growth factors) at four days (upper panels) and eight weeks (lower panels).
  • Figure 24 illustrates polarized light micrographs of H&E and ALP/TRAP stained FlexBone explants (25% HA-25% TCP, pre-absorbed with 400 ng rhBMP-2/7) showing active remodeling of FlexBone by osteoclasts (red TRAP stains) as well as new bone formation (blue ALP stain) at the periphery of the FlexBone material.
  • FB FlexBone
  • NB new bone
  • CB cortical bone
  • C callus
  • BM bone marrow
  • ALP alkaline phosphatase
  • TRAP tartrate- resistant alkaline phosphatase
  • H&E hematoxylin and eosin
  • HA hydroxyapatite
  • rhBMP recombinant human bone morphogenetic protein.
  • Figure 25 illustrates an X-ray radiograph and micro-CT analysis of a 12- week explant of FlexBone (25% HA-25% TCP, pre-absorbed with 400 ng rhBMP-2/7) showing the callus completely bridging over the defect area and extensive new bone formation surrounding the entire FlexBone graft.
  • RhBMP recombinant human bone morphogenetic protein
  • micro-CT micro-computed tomography.
  • Figure 26 illustrates microstructures and size distribution of ComHA versus CaIHA powders.
  • A SEM micrograph of ComHA powders showing porous aggregates of polycrystalline HA.
  • B Higher resolution SEM image of the circled area in (A) showing HA crystallites approximately 100 nm in size.
  • C Grinded CaIHA powders.
  • D Particle size distribution of the CaIHA as determined by sedimentation measurements for particles with diameters below 10 ⁇ m. Both SEM micrograph and the sedimentation measurement plot suggested a bimodal size distribution of CaIHA powders with most particles sized 5 ⁇ m or below and the larger grains over 10 ⁇ m in size.
  • Figure 27 illustrates as-prepared versus fully hydrated FlexBone.
  • Figure 28 illustrates freeze-dried FlexBone containing ComHA versus CaIHA.
  • A Stress-strain curves showing freeze-dried FlexBone containing 50% ComHA is stiffer than the one containing 50% CaIHA. Unconfined displacement-controlled (approximately 0.015 mm/s) compression test was performed on a high capacity MTS with a 100-kN load cell.
  • B and (C): SEM of the cross-section of freeze-dried CalHA-1-50 before and after being compressed.
  • the arrows in (C) and (E) indicate the direction of compression.
  • Figure 29 illustrates in vivo resorption and osteogenic differentiation of bone marrow cells supported by FlexBone ComHA- 1-40.
  • A SEM micrograph of a composite (pre-seeded with 20,000-cells/cm 2 BMSC) retrieved 28 days after SC implantation in rat;
  • B SEM micrograph of a composite (without pre-seeded BMSC) retrieved 14 days after SC implantation in rat;
  • C XRD of the explanted sample shown in (A), with diffraction patterns matching with that of the commercial HA powder;
  • D ALP staining (red) of a 12- ⁇ m frozen section of an explanted composite (pre-seeded with 5*10 3 cells/cm 2 BMSC) on day 14. Magnification: 40Ox.
  • Hormonal therapies, small molecule inhibitors targeting key regulatory factors, and gene therapies that are commonly used for the treatment of musculoskeletal conditions typically do not provide instant relief of the symptoms of acute injuries and critical size defects. From this perspective, surgical reconstruction using proper bone grafts serves an important solution to traumatic defects induced by trauma, cancer, metabolic diseases and aging.
  • grafts There are three types of bone grafts, autogenic, allogenic and synthetic. Disadvantages associated with autogenic grafting procedures include donor site morbidity, the frequent need for a second operation and an inadequate volume of transplant material. Allogenic bone grafts suffer from significant failure rates, mechanical instability, and immunological rejections. Synthetic grafts may be used in the reconstructive repair of skeletal defects. Preferred embodiments of the invention relate to grafts that are engineered to possess appropriate mechanical properties and integrated with bony tissue with good long-term viability.
  • Osteoconductive bioceramics include of poly(methyl methacrylate) (PMMA)- based bone cement, and polylactic acid (PLA), polyglycolic acid (PGA) and their copolymers.
  • PMMA poly(methyl methacrylate)
  • PLA polylactic acid
  • PGA polyglycolic acid
  • the bioceramics generally suffer from low fracture toughness.
  • the average lifetime for PMMA bone cements that are used for bonding metal implants to bone in total joint replacement devices is ⁇ 5 years, primarily due to their limited capacity to integrate with the bony tissue.
  • the PLA/PGA scaffolds are poor binders for bone minerals and inefficient carriers for osteogenic growth factors.
  • Synthetic organic matrices can be designed to promote new bone formation.
  • hydrogel scaffolds that degrade in response to matrix metalloprotease activity permit cell and bony tissue ingrowth, and self-assembling peptide amphiphiles have been engineered to template the nucleation of hydroxyapatite in vitro as disclosed in Hartgerink et ah, Science 294, 1684-1688 (2001), incorporated herein by reference.
  • a common limitation of these bioactive polymer scaffolds, however, is that they are mechanically weak, thus they are limited to treating small non/low-weight bearing craniofacial defects.
  • the present invention contemplates a synthetic polymer and polymer-mineral composite grafts that provide structural support and mechanical stabilization to the site of fragile skeletal defects and simultaneously serve as a vehicle to locally deliver exogenous growth factors and cytokines to trigger proper host cell responses, promoting graft healing.
  • the disclosed composites are denoted as #Com/Cal-N-AP/FD, where # denotes the weight percentage of HA, Com for commercial HA, CaI for calcined HA, N for the type of hydrogel formulations (1, 2, 3 or 4), AP for as-prepared, and FD for freeze- dried.
  • 70Cal-4-AP represents as-prepared FlexBone with 70% calcined HA that is formed using hydrogel formulation 4
  • 40Com-3-FD represents freeze-dried FlexBone with 40% commercial polycrystalline HA that is formed using hydrogel formulation 3.
  • Other objectives include: combining exogenous signaling molecules in order to introduce to the microenvironment of a defect to promote graft healing characterized by the remodeling, osteointegration and vascular ingrowth of the grafts; retaining and releasing bioactive signaling molecules to and from a synthetic graft in a sustained manner; integrating multiple desirable features including the ability to retain bioactive signaling molecules, biodegradability and cell adhesive properties into polymeric graft designs; and integrating osteoconductive bone mineral with the polymer scaffold with structural integration and mechanical properties to emulate the composite scaffold of bone.
  • embodiments of the invention be limited to any particular mechanism; however, it is believed that autogenic and allogenic bone graft healing is initiated by an inflammatory response, followed by vascular invasion and recruitment of mesenchymal stem cells (MSCs), a process similar to fracture healing.
  • MSCs mesenchymal stem cells
  • the later phase of graft repair and remodeling varies between dense cortical bone grafts and porous cancellous bone grafts, osteoclasts and osteoblasts are involved.
  • the imbalance between resorption and bone formation can lead to graft failure.
  • new vessels are involved in osteogenesis and bone remodeling. They serve as a source of osteoblast and osteoclast precursors and signals for their recruitment.
  • VEGF Vascular endothelial growth factor
  • RTKL nuclear factor KB ligand
  • bone morphogenetic proteins members of the transforming growth factor- ⁇ (TGF- ⁇ ) superfamily, promote osteogenesis and fracture repair by inducing the differentiation of MSCs into bone-forming and cartilage-forming cells.
  • Recombinant human bone morphogenetic protein-2 (rhBMP-2 or BMP-2/7 heterodiamer) has been approved by the Food and Drug Administration for clinical use as an adjuvant for spinal fusion and fracture union. Like osteoclast bone resorption, it is believed that osteogenesis is also dependent on sufficient vascularization.
  • endochondral ossification begins with the proliferation and aggregation of non-differentiated MSCs, which migrate along with new blood vessels and differentiate into osteoprogenitor cells and eventually give rise to bone formation.
  • VEGF plays a role during this process.
  • the invention relates to incorporating an exogenous supply of BMP-2, BMP-2/7 heterodimer, RANKL, and VEGF to a synthetic bone graft in order to induce host cell responses and elicit the coordinated remodeling and osteointegration of the grafts with vascular ingrowth.
  • This combination of signals may either be introduced as recombinant proteins or delivered by gene therapy approaches.
  • these growth factors and cytokines may be immobilized directly on the synthetic grafts.
  • BMP-2, RANKL, and VEGF fail to be retained within a local delivery site.
  • a synthetic carrier effectively retains and locally releases these exogenous proteins in a sustained manner, preferably throughout the early stage (first 3-5 days) of fracture/graft healing when the condensation of mesenchymal stem cells and the initiation of callus formation occur.
  • Sulfated polysaccharides such as heparin have an affinity for a number of basic growth factors including BMPs and VEGF.
  • some embodiments of the invention relate to using polymer grafts functionalized with ionic domains bearing net charges opposite to those of the growth factors as a delivery vehicle for signaling molecules.
  • anionic domains are integrate into the synthetic graft to retain the basic recombinant growth factors such as, but not limited to, rhBMP-2 (pi: 9.3), rhVEGF165 (pi: 8.5), and rmRANKL (pi: 9.1, E. coli expressed),
  • the amount of anionic ligands that can be incorporated without causing phase-separation is limited.
  • the attempt of integrating high percentages of anionic monomers (> 10-20%) in the hydrogel copolymer would leave a significant amount of anionic monomers unpolymerized, making the determination of the actual content and distribution of the anionic ligands within the hydrogel network difficult.
  • This limitation combined with the non-biodegradability of the carbon network, makes the conventional polymethacrylamides or polymethacrylates less desirable for the design of bioactive polymer bone grafts.
  • Another object of embodiments of the invention relates to injectable and degradable organic-inorganic hybrid macromers sequentially grafted with bone mineral nucleation domains, anionic growth factor retention domains, and cell adhesion domains as the functional building blocks of a new class of bioactive bone grafts.
  • these hybrid macromers are modularly functionalized with the multiple functional domains using controlled ring-opening polymerization (ROP) and reverse addition fragmentation transfer (RAFT) polymerization in combination with efficient bioconjugation chemistries.
  • ROP controlled ring-opening polymerization
  • RAFT reverse addition fragmentation transfer
  • the inorganic component of bone, calcium phosphate and the various calcium apatites support functions of the skeleton including calcium homeostasis, protection of soft organs and structure and locomotion with muscle tissue.
  • the bending and compression strength of human bone correlates to bone mineral content.
  • the quantity and quality of the deposited mineral influences the mechanical properties of bone. Proteins such as osteopontin and bone sialoprotein bind to HA crystals, and embodiments of the invention contemplate the use of calcium phosphates as carriers for the delivery of growth factors.
  • the invention relates to integration of osteoinductive calcium apatite, particularly at high mineral content approximating that of human bone with the bioactive polymer bone grafts to enhance both the mechanical and biological performance of synthetic bone grafts.
  • a surface layer of HA with varying morphology and crystallinity provides mineral- polymer interfacial adhesion.
  • the invention relates to HA-binding peptides and there use to template the nucleation and growth of aggregates preferably HA aggregates.
  • the invention relates to covalently incorporating the HA- binding peptides to the mineral nucleation domain of the polymer graft to facilitate template- driven HA-mineralization in situ and prepare polymer-mineral composite grafts with substantial calcium apatite content.
  • the invention relates to polymer siloxanes, preferably octakis(dimethylsiloxy) octasilsesquioxane (POSS), even more preferably octahedral hydroxylated POSS, and even more preferably octahedral hydroxylated POSS substituted with biodegradable polylactide (PLA) as disclosed in U.S. Provisional Patent Application No. 60/925329, filed April 19, 2007.
  • PES octakis(dimethylsiloxy) octasilsesquioxane
  • POSS biodegradable polylactide
  • certain embodiments of the invention relate to a self-forming synthetic bone graft for fracture repair and cements that lead to better alignment and fixation between grafts and surrounding bony tissues upon heat activation.
  • the invention relates to core structures of a macromer that act as building blocks for the addition of various functional domains.
  • the macromer is an initiator for RAFT polymerizations.
  • the invention relates to Si-based nanoparticles that are anchors for grafting polymer domains in bone grafts.
  • the cross-linker could depend on the functional groups, preferably the terminal functional group, displayed on the side chains on the grafted polymer blocks.
  • the functional groups preferably the terminal functional group
  • the cross-linker could depend on the functional groups, preferably the terminal functional group, displayed on the side chains on the grafted polymer blocks.
  • POSS-(PLA n - co-pHEMA m ) 8 one can crosslink with a diisocyanate since the pHEMA block contains hydroxyl side chains.
  • POSS-(PLA n ) 8 or POSS-(PLA n -CO- pHEMA m ) 8 with alkylacrylates containing hydroxyl side chains as illustrated in Figure 12.
  • Figure 13 illustrates how one can incorporate HA-binding peptides to template the nucleation and growth of HA.
  • hydrogels such as poly(2-hydroxyethyl methacrylate), pHEMA, and functionalized derivatives are useful in a wide range of biomedical applications.
  • these hydrogel polymers may be utilized in ophthalmic devices, soft tissue engineering scaffolds, carriers for drug or growth factor delivery, dental cements and medical sealants.
  • HA hydroxyapatite
  • HEMA poly(2-hydroxyethyl methacrylate)
  • HA hydroxyapatite
  • a preferred approach involves the formation of crosslinked pHEMA hydrogel in the presence of different types of HA powder using viscous aqueous ethylene glycol as a solvent.
  • these composites termed “FlexBone” are elastic and have unexpectedly high fracture resistance under physiological compressive loadings. Tailored microstructural property and compressive behavior of the composites can be achieved by the selective use of HA powder of varied sizes and aggregation and the composition of the organic component(s).
  • the preparation of a class of elastomeric pHEMA-HA composite, FlexBone, comprising a high percentage (up to 70%) of osteoconductive HA is disclosed. These materials are able to withstand up to several hundred-megapascal compressive loads and over 70-80% strain without exhibiting brittle fracture despite having high mineral contents.
  • the pre-polymer hydrogel cocktail formulation and the post-solidification processing conditions affect the compressive strength and elasticity of the FlexBone composites.
  • the viscosity of ethylene glycol, the co-solvent used along with water during the fabrication of FlexBone composites facilitated the dispersion of HA within the hydrogel scaffold, thereby preventing the HA particles from settling to the bottom of the mold during solidification.
  • the high-boiling point of ethylene glycol also contributed to the long-lasting elasticity observed with the as-prepared FlexBone composite crosslinked in high-ethylene glycol-content media.
  • the compressive behavior of the FlexBone composite is dependent on its mineral content, a property that is useful in tailoring FlexBone for clinical applications ranging from craniofacial defects to weight-bearing fractures.
  • the work under the force-strain curves of FlexBone samples increased with increasing mineral content, suggesting that FlexBone samples with higher percentages of HA are generally stiffer, tougher, and stronger.
  • This trend as representatively shown in Figure 3, applied to FlexBone containing calcined HA powder as well and is in agreement with those observed with natural bone, where the tensile Young's modulus of compact bone shows a strong positive correlation with the mineral content.
  • the force-strain curves obtained with freeze-dried mineralized samples are characteristically less smooth than those obtained with unmineralized pHEMA control gel or as-prepared composite gels. This may be due in part to the micropores generated by the removal of water during the freeze-drying process.
  • a preferred synthetic bone graft is designed to fill an area of defect to provide structural stabilization and to promote the healing and repair of the skeletal lesion.
  • the synthetic grafts eventually remodel and become replaced by newly synthesized bone. From this perspective, biodegradability, osteoconductivity and osteoinductivity of the synthetic bone grafts are desirable along with mechanical strength and elastomeric properties that facilitate its surgical fitting to the defect site.
  • One object of embodiments of the invention is to provide biodegradability of the organic matrix of the composite grafts in order to enhance the in vivo dissolution rate of the osteoconductive mineral component (e.g. by using a more soluble ⁇ -tricalcium phosphate, ⁇ - TCP, to the HA mineral phase), and locally retaining and releasing osteoinductive growth factors and cytokines on and from the synthetic scaffold.
  • Embodiments of the invention contemplate lightweight pHEMA-HA composites containing between 40%-80% HA and even more preferably 50%-80% HA. These composites may be prepared using a variety of hydrogel formulations and HA particles.
  • the adjustable parameters of the composite formulations allowed engineered FlexBone with a range of compressive strength and stiffness. FlexBone composites exhibit strong organic-inorganic material integration throughout the 3-D network, and did not undergo brittle fracture under high compressive stress despite their high mineral content. The elasticity of the as-prepared composites facilitate better fitting (by compression) of FlexBone into an area of bone defect.
  • the invention relates to polymerizable composite formulations injected into a defect site to allow for in situ solidification.
  • a synthetic graft possessing elastomeric properties may accommodate the inherent micro movement of bone, particularly at the bone-graft interface, thus reducing potential graft failure.
  • the fracture resistant compressive behavior of FlexBone and its ability to slowly reabsorb and template the osteoblastic differentiation of BMSC in vivo makes FlexBone a preferred candidate for craniofacial applications and for treatment of bony defects requiring moderate load-bearing capability.
  • the invention relates to antibiotics and bioactive signaling molecules related to osteoblast differentiation attached to composite graphs disclosed herein.
  • the signaling molecules may be covalently attached to or non-covalently trapped within the hydrogel scaffold of the composite.
  • a range of in vivo resorption rates may also be engineered via the use of HA in combination with other calcium phosphate particles, such as ⁇ -TCP, that have desired in vivo dissolution rates for remodeling.
  • the invention relates to loading FlexBone with bone marrow stem cells prior to surgical implantation.
  • a Flexbone graph loaded with cells can be applied to a removed femoral segmental as provided in Example 9.
  • the loading of grafts with bone marrow stem cells prior to implantation enhances the ability of the graph to integrate with host tissue, vascularize, and heal.
  • Further embodiments of the invention relate to 1) pre-load growth factors and cytokines, gene vectors, or retroviruses on Flexbone prior to surgical implantation; 2) pre-load FlexBone with cells prior to implantation; or 3) pre-load growth factors and cytokine, gene vectors, retroviruses plus cells in FlexBone prior to implantation. All these approaches may optionally be combined with the pre-drilling holes in FlexBone.
  • the gene vector encodes BMP-2, BMP-2/7 heterodiamer, RANKL and VEGF.
  • the gene vectors are recombinant adeno-associated viruses, rAA-BMP-2, rAA- BMP-2/7 heterodiamer, ⁇ AA-RANKL and rAA-VEGF prepared as disclosed or appropriately modified in Ito et al., Nature Medicine 11(3):291-297 (2005).
  • a "material” means a physical substance preferably a solid, but it is not intended to be limited to a solid material. It is also not intended to be limited to those substances that are actually used in the manufacture or production of a device.
  • conjugate refers to any compound that has been formed by the joining of two or more moieties.
  • a "moiety” or “group” is any type of molecular arrangement designated by formula, chemical name, or structure.
  • a conjugate is said to comprise one or more moieties or chemical groups. This means that the formula of the moiety is substituted at some place in order to be joined and be a part of the molecular arrangement of the conjugate.
  • moieties may be directly covalently joined, it is not intended that the joining of two or more moieties must be directly to each other.
  • a linking group, crosslinking group, or joining group refers any molecular arrangement that will connect the moieties by covalent bonds such as, but are not limited to, one or more amide group(s), may join the moieties.
  • the conjugate may be unsubstituted, the conjugate may have a variety of additional substituents connected to the linking groups and/or connected to the moieties.
  • Siloxane moieties are molecular arrangements containing silicon-oxygen bonds.
  • the siloxane moieties are caged structures.
  • substituted means at least one hydrogen atom of a molecular arrangement is replaced with a substituent.
  • substituents may be further substituted with one or more of the above substituents, such that the substituent comprises a substituted alky, substituted aryl, substituted arylalkyl, substituted heterocycle, or substituted heterocyclealkyl.
  • R 3 and R b in this context may be the same or different and, independently, hydrogen, alkyl, haloalkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, heterocycle, substituted heterocycle, heterocyclealkyl or substituted heterocyclealkyl.
  • unsubstituted refers to any compound does not contain extra substituents attached to the compound.
  • unsubstituted compound refers to the chemical makeup of the compound without extra substituents, e.g., the compound does not contain protecting group(s).
  • unsubstituted proline is a proline amino acid even though the amino group of proline may be considered disubstituted with alkyl groups.
  • alkyl means any straight chain or branched, non-cyclic or cyclic, unsaturated or saturated aliphatic hydrocarbon containing from 1 to 10 carbon atoms, while the term “lower alkyl” has the same meaning as alkyl but contains from 1 to 6 carbon atoms.
  • the term “higher alkyl” has the same meaning as alkyl but contains from 2 to 10 carbon atoms.
  • saturated straight chain alkyls include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-septyl, n-octyl, n-nonyl, and the like; while saturated branched alkyls include, but are not limited to, isopropyl, sec-butyl, isobutyl, tert- butyl, isopentyl, and the like. Cyclic alkyls may be obtained by joining two alkyl groups bound to the same atom or by joining two alkyl groups each bound to adjoining atoms.
  • saturated cyclic alkyls include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like; while unsaturated cyclic alkyls include, but are not limited to, cyclopentenyl and cyclohexenyl, and the like.
  • Cyclic alkyls are also referred to herein as a "homocycles" or "homocyclic rings.”
  • Unsaturated alkyls contain at least one double or triple bond between adjacent carbon atoms (referred to as an "alkenyl” or “alkynyl", respectively).
  • Representative straight chain and branched alkenyls include, but are not limited to, ethylenyl, propyl enyl, 1-butenyl, 2-butenyl, isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl- 1-butenyl, 2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like; while representative straight chain and branched alkynyls include, but are not limited to, acetylenyl, propynyl, 1- butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl, 3-methyl-l-butynyl, and the like.
  • aryl as used herein, means any aromatic carbocyclic moiety such as, but not limited to, phenyl or naphthyl.
  • arylalkyl means any alkyl having at least one alkyl hydrogen atoms replaced with an aryl moiety, such as benzyl, but not limited to, — (CH 2 ) 2 phenyl, — (CH 2 ) 3 phenyl, — CH(phenyl) 2 , and the like.
  • halogen refers to any fluoro, chloro, bromo, or iodo moiety.
  • haloalkyl refers to any alkyl having at least one hydrogen atom replaced with halogen, such as trifluoromethyl, and the like.
  • heteroaryl refers to any aromatic heterocycle ring of 5- to 10 members and having at least one heteroatom selected from nitrogen, oxygen and sulfur, and containing at least 1 carbon atom, including, but not limited to, both mono- and bicyclic ring systems.
  • heteroaryls include, but are not limited to, furyl, benzofuranyl, thiophenyl, benzothiophenyl, pyrrolyl, indolyl, isoindolyl, azaindolyl, pyridyl, quinolinyl, isoquinolinyl, oxazolyl, isooxazolyl, benzoxazolyl, pyrazolyl, imidazolyl, benzimidazolyl, thiazolyl, benzothiazolyl, isothiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, cinnolinyl, phthalazinyl, or quinazolinyl.
  • heteroarylalkyl means any alkyl having at least one alkyl hydrogen atom replaced with a heteroaryl moiety, such as ⁇ CH 2 pyridinyl, ⁇ CH 2 pyrimidinyl, and the like.
  • heterocycle or “heterocyclic ring”, as used herein, means any 4- to 7- membered monocyclic, or 7- to 10-membered bicyclic, heterocyclic ring which is either saturated, unsaturated, or aromatic, and which contains from 1 to 4 heteroatoms independently selected from nitrogen, oxygen and sulfur, and wherein the nitrogen and sulfur heteroatoms may be optionally oxidized, and the nitrogen heteroatom may be optionally quaternized, including bicyclic rings in which any of the above heterocycles are fused to a benzene ring.
  • the heterocycle may be attached via any heteroatom or carbon atom.
  • Heterocycles may include heteroaryls exemplified by those defined above.
  • heterocycles may also include, but are not limited to, morpholinyl, pyrrolidinonyl, pyrrolidinyl, piperidinyl, hydantoinyl, valerolactamyl, oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydropyridinyl, tetrahydroprimidinyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, tetrahydropyrimidinyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, and the like.
  • heterocyclealkyl means any alkyl having at least one alkyl hydrogen atom replaced with a heterocycle, such as — CH 2 morpholinyl, and the like.
  • heterocycle or "homocyclic ring”, as used herein, means any saturated or unsaturated (but not aromatic) carbocyclic ring containing from 3-7 carbon atoms, such as, but not limited to, cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclohexene, and the like.
  • alkylamino means at least one alkyl moiety attached through a nitrogen bridge (i.e., ⁇ N-(alkyl)N, such as a dialkylamino)) including, but not limited to, methylamino, ethylamino, dimethylamino, diethylamino, and the like.
  • alkyloxy means any alkyl moiety attached through an oxygen bridge (i.e., --O-alkyl) such as, but not limited to, methoxy, ethoxy, and the like.
  • alkylthio means any alkyl moiety attached through a sulfur bridge (i.e., --S-- alkyl) such as, but not limited to, methylthio, ethylthio, and the like
  • alkenyl means a unbranched or branched hydrocarbon chain having one or more double bonds therein.
  • the double bond of an alkenyl group can be unconjugated or conjugated to another unsaturated group.
  • Suitable alkenyl groups include, but are not limited to (C 2 -Cg)alkenyl groups, such as vinyl, allyl, butenyl, pentenyl, hexenyl, butadienyl, pentadienyl, hexadienyl, 2-ethylhexenyl,2-propyl-2-butenyl,4-(2-methyl-3-butene)-pentenyl.
  • An alkenyl group can be unsubstituted or substituted with one or two suitable substituents.
  • alkynyl means unbranched or branched hydrocarbon chain having one or more triple bonds therein.
  • the triple bond of an alkynyl group can be unconjugated or conjugated to another unsaturated group.
  • Suitable alkynyl groups include, but are not limited to, (C 2 -Cg)alkynyl groups, such as ethynyl, propynyl, butynyl, pentynyl, hexynyl, methylpropynyl, 4-methyl-l -butynyl, 4-propyl-2-pentynyl-, and 4-butyl-2-hexynyl.
  • An alkynyl group can be unsubstituted or substituted with one or two suitable substituents
  • salts refers to any salt that complexes with identified compounds contained herein.
  • examples of such salts include, but are not limited to, acid addition salts formed with inorganic acids (e.g. hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, and the like), and salts formed with organic acids such as, but not limited to, acetic acid, oxalic acid, tartaric acid, succinic acid, malic acid, fumaric acid, maleic acid, ascorbic acid, benzoic acid, tannic acid, pamoic acid, alginic acid, polyglutamic, acid, naphthalene sulfonic acid, naphthalene disulfonic acid, and polygalacturonic acid.
  • inorganic acids e.g. hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, and the like
  • organic acids such as, but not limited to, acetic acid, o
  • Salt compounds can also be administered as pharmaceutically acceptable quaternary salts known by a person skilled in the art, which specifically include the quaternary ammonium salts of the formula ⁇ NR,R',R" + Z " , wherein R, R', R" is independently hydrogen, alkyl, or benzyl, and Z is a counter ion, including, but not limited to, chloride, bromide, iodide, alkoxide, toluenesulfonate, methylsulfonate, sulfonate, phosphate, or carboxylate (such as benzoate, succinate, acetate, glycolate, maleate, malate, fumarate, citrate, tartrate, ascorbate, cinnamoate, mandeloate, and diphenylacetate). Salt compounds can also be administered as pharmaceutically acceptable pyridine cation salts having a substituted or unsubstituted partial formula:
  • Z is a counter ion, including, but not limited to, chloride, bromide, iodide, alkoxide, toluenesulfonate, methylsulfonate, sulfonate, phosphate, or carboxylate (such as benzoate, succinate, acetate, glycolate, maleate, malate, fumarate, citrate, tartrate, ascorbate, cinnamoate, mandeloate, and diphenylacetate).
  • carboxylate such as benzoate, succinate, acetate, glycolate, maleate, malate, fumarate, citrate, tartrate, ascorbate, cinnamoate, mandeloate, and diphenylacetate.
  • reactive groups refer to nucleophiles, electrophiles, or radically active groups, i.e., groups that react in the presence of radicals.
  • a nucleophile is a moeity that forms a chemical bond to its reaction partner (the electrophile) by donating both bonding electrons. Electrophile accept these electrons.
  • Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge on an element and displaces the group it is bonded to. Alternatively nucleophiles may take part in substitution of carbonyl group.
  • Carboxylic acids are often made electrophilic by creating succinyl esters and reacting these esters with aminoalkyls to form amides.
  • nucleophilic groups are thiolalkyls, hydroxylalkys, primary and secondary amines, and carbon nucleophiles such as enols and alkyl metal complexes.
  • Other preferred methods of ligating proteins, oligosaccharides and cells using reactive groups are disclosed in Lemieux & Bertozzi, Trends in Biotechology 16 (12): 506-513 (1998), incorporated herein by reference.
  • one provides reactive groups for the Staudinger ligation, i.e., "click chemistry" with an azide comprising moiety and an alkynyl reactive groups to form triazoles.
  • a "polymer” refers to any covalent arrangement of atoms made up of repeatedly linked subunits. Within certain embodiments, it is preferred that the number of repeating moieties is three or more or greater than 10.
  • the linked moieties may be identical in structure or may have variation of structure, i.e., co-polymer.
  • the polymer is made up of moieties linked by ester groups, i.e., polyester. Polyesters include polymer architecture obtained through stereoselective polymerizations.
  • Polylactone means a polyester of any cyclic diester, preferably the glycolide the diester of glycolic acid, lactide, the diester of 2-hydroxypropionic acid, ethylglycolide, hexylglycolide, and isobutylglycolide, which can be produced in chiral and racemic forms by, e.g., fermentation of corn.
  • Metal alkoxide catalysts may be used for the ring-opening polymerization (ROP) of lactones. In the presence of chiral catalysts, each catalyst enantiomer preferentially polymerizes one lactone stereoisomer to give polymer chains with isotactic domains.
  • a "peptide” refers to compounds containing two or more amino acids linked by the carboxyl group of one amino acid to the amino group of another. It is contemplated to include enzymes, receptors, proteins and recombinant proteins. It is contemplated that they may be purified and/or isolated from natural sources or prepared by recombinant or synthetic methods. The amino acids may be naturally or non-naturally occurring or substituted with substituents.
  • a "composite” refers to two or more constituent compositions that remain distinct on a macroscopic level, preferably approaching nanometer dimensions, within a finished structure.
  • the composite material has a polymer component and an aggregate component. It is not intended that embodiments of the invention be limited to any particular mechanism, but it is believed that the molecular properties of the polymer, particularly the hydrophobicity of monomer subunits provides desirable adherence of the aggregates to the polymer matrix.
  • the "polymer matrix” refers to the surrounding polymer within which aggregates are contained. It is contemplated that such a matrix may be porous or non-porous.
  • hydroxyalkyl acrylate refers to a compound having the general formula: wherein R 1 is hydrogen or alkyl and n is 1 to 22.
  • a preferred hydroxyalkyl acrylate is 2- hydroxyethyl methacrylate, where R 1 is methyl and n is 2, having the formula:
  • monomer subunits of a polymer refers to the repeating structure that results from the polymerization process of monomers.
  • subunits of 2-hydroxyethyl methacrylate have the following repeating representative structural formula:
  • siloxane macromer refers to a siloxane substituted with three or more crosslinking groups and/or polymer(s).
  • the linking groups and/or polymers may be the same or different.
  • cross-linker refers to any variety of molecular arrangements that upon a chemical reaction covalently bonds one molecular entity, e.g., polymer, monomer, biomolecule, and/or macromer, to another. It is intended to include crossliking between different molecular entities.
  • a cross-linker comprises a linking group terminally substituted with a reactive group, or two or more reactive groups. The two reactive groups may be different. Examples of preferred cross-linkers are polyethylene glycol diacrylate, polyethylene glycol diisocyanate, and hexamethylene diisocyanate.
  • a "linking group” refers to any molecular arrangement for connecting chemical moieties. Examples include disubstituted groups such as, but not limited to, alkyl, substituted alkyl, polyethylene glycol, substituted polyethylene glycol, alkylamine, substituted alkylamine, polyalkylamine, substituted polyalkylamine, alkylthiol, substituted alkylthiol polyalkylthiol, substituted polyalkylthiol, alkylamide, substituted alkylamide, polyalkylamide, substituted polyalkylamide, alkylthioester, substituted alkylthioester, polyalkyl thioester, a substituted polyalkylthioester, alkylthioamide, substituted alkylthioamide, polyalkylthioamide, substituted alkylthioamide groups and combinations thereof.
  • hydroxyl refers to an oxygen atom covalently bound to a hydrogen atom. It is contemplated that the oxygen atom may be further covalently or non-covalently bound to other atoms, including, but not limited to, carbon, metals, and metalloids. It is also contemplated that hydroxyl may be a hydroxyl ion.
  • alkyl means any straight chain or branched, non-cyclic or cyclic, unsaturated or saturated aliphatic hydrocarbon containing from 1 to 10 carbon atoms, while the term “short chain alkyl” has the same meaning as alkyl but contains from 1 to 4 carbon atoms.
  • long chain alkyl has the same meaning as alkyl but contains from 5 to 22 carbon atoms.
  • saturated straight chain alkyls include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-septyl, n-octyl, n-nonyl, and the like; while saturated branched alkyls include, but are not limited to, isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, and the like. Cyclic alkyls may be obtained by joining two alkyl groups bound to the same atom or by joining two alkyl groups each bound to adjoining atoms.
  • saturated cyclic alkyls include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like; while unsaturated cyclic alkyls include, but are not limited to, cyclopentenyl and cyclohexenyl, and the like.
  • Cyclic alkyls are also referred to herein as a "homocycles" or "homocyclic rings.”
  • Unsaturated alkyls contain at least one double or triple bond between adjacent carbon atoms (referred to as an "alkenyl” or “alkynyl", respectively).
  • Representative straight chain and branched alkenyls include, but are not limited to, ethyl enyl, propylenyl, 1-butenyl, 2-butenyl, isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl- 1-butenyl, 2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like; while representative straight chain and branched alkynyls include, but are not limited to, acetylenyl, propynyl, 1- butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl, 3-methyl-l-butynyl, and the like.
  • aggregates refers to a collection of atoms or molecules that form a collective mass. It is intended that the atoms can be a part of organic molecules, alloys, salts, metallic salts, and minerals. It is not intended that the aggregate be limited to having any specific shape. In preferred embodiments, aggregates have a preferred size, i.e., largest diameter, of between or 50 nanometers and 500 micrometers, or greater than 50 nanometers.
  • Calcium phosphate aggregates refers to aggregates containing calcium or calcium ions together with phosphate, polyphosphate, orthophosphates, metaphosphates, pyrophosphates, hydroxyl or combinations thereof. Examples include hydroxyapatite and tricalcium triphosphate of both alpha and beta crytalline forms.
  • salts refer to an array of anionic and cationic atoms or molecules. It is not intended to be limited to those that contain metal atoms.
  • minerals refers to arrays of atoms that contain metal or metalloids and a substantial amount of nonmetal atoms. These arrays may contain ionic, coordinate or covalently bound atoms or complexes.
  • Preferred minerals contain calcium, more preferably calcium phosphate such as beta-tricalcium phosphate, and even more preferably calcium hydroxyapatite.
  • elastic materials refer to materials returning to or capable of returning substantially to an initial form or state after a substantial deformation, preferably more than a 10% deformation by volume without a fracture, and even more preferably a 20% deformation by volume without a fracture. It is not intended to refer to brittle material that fractures upon deformation of volume despite the fact that the material may have a very low and small elastic range.
  • materials disclosed herein are elastic upon applying a compressive load of up to 1.4 MPa, more preferably of up to 2.6 MPa, and even more preferably up to 7.0 MPa and greater.
  • a "fracture” refers to a break, rupture, or crack.
  • materials disclosed herein do not fracture at forces up to 28 MPa, more preferably they do not fracture between 28 and 524 MPa, and even more preferably they do not fracture between 150 and 500 MPa.
  • substituted means at least one hydrogen atom of a molecular arrangement is replaced with a substituent.
  • substituents may be further substituted with one or more of the above substituents, such that the substituent comprises a substituted alky, substituted aryl, substituted arylalkyl, substituted heterocycle, or substituted heterocyclealkyl.
  • R 3 and R b in this context may be the same or different and, independently, hydrogen, alkyl, haloalkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, heterocycle, substituted heterocycle, heterocyclealkyl or substituted heterocyclealkyl.
  • unsubstituted compound refers to the chemical makeup of the compound without extra substituents.
  • unsubstituted proline is a proline amino acid even though the amino group of proline may be considered disubstituted with alkyl groups.
  • ethylene glycol refers to a compound represented by the formula HO(CH 2 CH 2 O) n H, where n is 1.
  • Polyethylene glycol refers to said formula where n is greater than 1, preferably providing a compound with an overall molecular weigh of less than 40,000.
  • a polymer subunit of polyethylene glycol is -(CH 2 CH 2 O) n - where n is greater than 1.
  • a "bulk” material refers to a material that is consistently homogeneous within the interior of the material and at or near the surface of the material. It is not intended that the material necessary be homogeneous on or near the surface. The atoms at or near the surface may be oxidized because of exposure to the atmosphere. It is also contemplated that a bulk material may be chemically modified in order to facilitate contacting or connecting other materials or in order to grow other material layers; however, it is not contemplated that these surface modifications significantly alter the composition of the interior of the bulk material.
  • a “homogeneous” material referes to the atomic and molecular constituents that make up the material having substantially the same distribution throughout the material considering a 1 millimeter unit cell or less, preferably a 100 micrometer unit cell or less.
  • a "pore" refers to an opening through which fluid may pass.
  • a pore is created in composite materials disclosed herein using a drill or laser by channeling through the material creating holes of substantially similar dimensions.
  • cells refer to the structural unit of an organism consisting of a nucleus and organelles surrounded by a semipermeable cell membrane. It is not intended to be limited to live or functioning cells.
  • the invention relates to materials that contain, incorporate, attach, or bind stem cells, hematopoieitic stem cells, endothelial cells, adipocytes, smooth muscle cells, reticular cells, osteoblasts, stromal fibroblasts, osteocytes and even more preferably, bone marrow stromal cells and mesenchymal stem cells.
  • bone marrow cells refers to both bone marrow stems cells and the cells bone marrow stem cells differentiate into.
  • Examples of bone marrow stem cells include hematopoietic stem cells and mesenchymal stem cells.
  • examples of other bone marrow cells include, white blood cells (leukocytes), red blood cells (erythrocytes), platelets (thrombocytes), osteoblasts, chondrocytes, and myocytes.
  • saccharide means a sugar or substituted sugar exemplified by, but not limited to glucoside, glucoside tetraacetate, mannoside, mannoside tetraacetate, galactoside, galactoside tetraacetate, alloside, alloside tetraacetate, guloside, guloside tetraacetate, idoside, idoside tetraacetate, taloside, taloside tetraacetate, rhamnoside, rhamnoside triacetate, maltoside, maltoside heptaacetate, 2,3-desoxy-2,3-dehydromaltoside, 2,3-desoxy-2,3-dehydromaltoside pentaacetate, 2,3-desoxymaltoside, lactoside, lactoside tetraacetate, 2,3-desoxy-2,3- dehydrolactoside, 2,3-desoxy-2,3-dehydrolactoside pentta
  • a "biomolecule” refers to substances found or produced, engineered or naturally, in living organisms. It is not intended to be limited to actually obtaining the molecule from a living organism, i.e., the biomolecule may be made synthetically (in vitro). Examples include, but are not limited to, peptides, proteins, enzymes, receptors, substrates, lipids, antibodies, antigens, and nucleic acids.
  • a “biodegradable” material refers to a material that breaks down all or a portion of the material into smaller components when interfaced with a living environment, preferably for the purpose of expelling non-naturally occurring components.
  • cytokine referes to a protein or glycoprotein that is used in an organism as signaling compounds. It is intended to include homologues and synthetic versions. Examples include the IL-2 subfamily, non-immunological such as erythropoietin (EPO) and thrombopoietin (THPO), the interferon (IFN) subfamily, the IL-IO subfamily, IL-I and IL- 18, CC chemokines (CCL)-I to -28, and CXC chemokines.
  • EPO erythropoietin
  • THPO thrombopoietin
  • a "gene vector” refers to any sequence of nucleic acid that codes for a particular protein, hi a preferred embodiment, the gene vector is a plasmid or virus, such as a retrovirus, adenovirus, adeno-associated virus, herpesvirus, or lentivirus. These may be recombinant. With regard to recombinant adenovirus vectors, it is preferred that the vector is an "empty-Ad", i.e., Ad genes are eliminated, since they provide a decreased antigenic load. Recombinant adenoviruses are typically delivered with helperviruses that replicate and express multiple Ad genes when present as described in Chamberlain et al., U.S. Patent No.
  • a "subject” refers to any animal, preferably a human patient, livestock, or domestic pet.
  • hydrophilic group refers to any molecular arrangement that contains enough atoms that participate in hydrogen bonding to dissolve in water, i.e., water-soluble.
  • hydrophilic groups include, but are not limited to, hydroxyl, carboxylate, ether, amine, amide, sulfate, sulfite, phosphate, polyphosphate groups, and corresponding acids and salts thereof.
  • a preferred hydrophilic linking group is polyethylene glycol.
  • a "reactive group” refers to a molecular arrangement that spontaneously forms covalent bonds when mixed with a compound that has a corresponding functional group.
  • examples are vinyl groups, which react with radicals.
  • Other examples include nucleophiles and electrophiles, which react with each other.
  • compounds with acrylic groups react with radicals.
  • nucleophiles may take part in the substitution of electron withdrawing groups on a carbonyl.
  • carboxylic acids are often made electrophilic by creating succinyl esters and reacting these esters with aminoalkyls to form amides.
  • Other common nucleophilic groups are thiolalkyls, hydroxylalkyls, primary and secondary amines, and carbon nucleophiles such as enols and alkyl metal complexes.
  • a "radical” refers to species with a single, unpaired electron. Radical species can be electrically neutral, but it is not intended that the term be limited to electrically neutral species, in which case they are referred to as free radicals. Pairs of electrically neutral radicals may be formed via homolytic bond breakage. Heating chlorine, Cl 2 , forms chlorine radicals, Cl*. Similarly, peroxides form oxygen radicals and peresters fragment to acyl radicals, which may decompose to lose carbon dioxide to give carbon radicals. Azo compounds eject nitrogen to give a pair of carbon radicals. Many polymers may be made by the chain radical addition of substituted vinyl moieties with radicals.
  • a "radical inhibitor” refers to any additive including but not limited to a compound or protein that is added to a chemical for inhibiting the self-induced, free-radical polymerization of said chemical.
  • radical initiator refers to any compound that can produce radical species, i.e. molecules or atoms with available, unpaired electrons, under mild chemical reaction conditions and promote radical polymerization reactions. While not limiting the present invention to any particular compound or class of compounds, radical initiators include but are in no way limited to halogen free radicals, azo compounds and organic peroxides. Osteogenesis
  • Bone formation is highly coordinated, beginning with the commitment of mesenchymal stem cells (MSCs) to an osteogenic fate and their subsequent differentiation and maturation into the major bone-forming cells, the osteoblasts.
  • MSCs mesenchymal stem cells
  • This sequential progression is regulated, among other influences, by a diverse repertoire of growth and adhesive factors acting in autocrine/paracrine manners at specific developmental stages.
  • FGF fibroblast growth factor
  • FGFR fibroblast growth factor
  • HSPGs cell- surface heparin sulfate proteoglycans
  • FGF fibroblast growth factors
  • FGFR fibroblast growth factor receptors
  • Surgery is the preferred treatment for patients who have a neoplastic process affecting the mandible. If the lesion is benign but has compromised the integrity of the mandible, resection and reconstruction of the mandible is appropriate. If the lesion is malignant and has gained access to the cancellous bone, resection is also appropriate to obtain adequate surgical margins. Segmental composite mandibulectomy is a preferred treatment.
  • the invention relates to the use of composites disclosed herein that contain cells and biomolecules that promote osteogenesis as a transport disc to grow new bone.
  • Transport disc osteogenesis is used to grow new bone across a defect where bone has been lost.
  • a segment of bone is osteotomized adjacent to the defect and moved slowly and continuously across the defect by the use of a mechanical device. New bone fills in between the two bone segments.
  • the piece of bone or material being moved or transported is referred to as the transport disc. Large populations of osteogenic cells in an intact periosteum will be present in patients where a simple mandibulectomy has been done with little associated soft-tissue resection.
  • siloxanes including silsesquioxanes and metallasiloxanes
  • metallasiloxanes are described in Purkayastha & Baruah, Applied Organometallic Chemistry 2004, 18, 166-175.
  • Silsesquioxane are compounds of an approximate formula of about RSiOi. 5 , where R is any moiety but typically an alkyl, aryl, or substituted conjugate thereof.
  • the compounds may assume a myriad of structures, including random, ladder, cage and partial cage structures (see Figure 14B).
  • Silsesquioxanes are also sometimes termed ormosils (organically modified siloxanes).
  • a preferred silsesquioxane is shown in Figure 14A.
  • To prepare mono-substituted silsesquioxane there are several conventional synthetic routes. For example, the reaction of HSiCh with PhSiCl 3 results in the formation of PhH 7 Sis0i 2 via a co-hydrolysis reaction.
  • a second route uses substitution reactions at a silicon center with the retention of the siloxane cage leading to structural modifications of silsesquioxane.
  • POSS Polyhedral Oligomeric Silsesquioxanes
  • POSS chemicals may be incorporated into common plastics via co-polymerization, grafting, or blending.
  • Metallasiloxanes are siloxanes in which some of the silicon atoms have been replaced by a metal. Incorporation of metal into a siloxane framework can lead to two- and three- dimensional or linear networks. Metallasiloxanes may be derived from silanediols, disilanol, silanetriols and trisilanols. For example, the transesterif ⁇ cation reaction of Ti(O-IPr) 4 with sterically hindered silanediol ⁇ (t-Bu0-) 3 Si0 ⁇ 2 Si(0H) 2 gives cyclic siloxane of the following formula:
  • Such compounds are made of eight-membered rings having the composition Ti 2 Si 2 O 4 . Both silicon and titanium atoms in the molecule exhibit regular tetrahedral geometry.
  • the corresponding zirconium compound [1-Bu 2 Si(O)OZrCh] 2 may be prepared from the reaction between the dilithium salt of t-Bu 2 Si(OH) 2 and ZrCl 4 .
  • Cyclopentadienyl-substituted titanasiloxane [t-Bu 2 Si(O)OTiCpCl] 2 may be prepared directly by the reaction of CpTiCh with t-Bu 2 Si(OLi) 2 .
  • the reaction of the silanediol Ph 2 Si(OH) 2 with the zirconium amido derivative Zr(NEt 2 ) 4 leads to the formation of the dianonic tris-chelate metallasiloxane [NEt 2 H 2 J 2 [(Ph 4 Si 2 Os) 3 Zr].
  • zirconocene six oxygen atoms in a distorted octahedral geometry coordinate the central zirconium atom.
  • Disilanols may also be used as building blocks for a variety of metallasiloxanes.
  • the disilanols are capable of chelating to form six-membered rings containing the central metal. The reactions lead to Group 4 metallasiloxanes from disilanols.
  • metallasiloxane derivatives of Group 5, Group 7, Group 9 and main group metals may be prepared from disilanols. Reactions of silanediol and disilanols with titanium halides or titanium amides give cyclic titanasiloxanes. Three-dimensional titanasiloxanes can be prepared by the reaction of the titanium amide with silanol or silanediol.
  • Cubic titanasiloxanes can be prepared by a single-step synthesis from the reaction of titanium orthoesters and silanetriols.
  • cubic metallasiloxanes, M 4 Si 4 O 12 polyhedrons are present.
  • oligomeric silsesquioxanes The preparation of oligomeric silsesquioxanes is generally described in Li et al., (2002) Journal of Inorganic and Organometallic Polymers 11, 123-154. Reactions leading to the formation of POSS may be characterized depending on the nature of the starting materials employed. One group includes the reactions giving rise to new Si-O-Si bonds with subsequent formation of the polyhedral cage framework.
  • This class of reactions assembles polyhedral silsesquioxanes from monomers of the XSiY 3 type, where X is a chemically stable substituent (for example, CH 3 , phenyl, or vinyl), and Y is a highly reactive substituent (for example, Cl, OH, or OR) as represented in Equation 1 : nXSiY 3 +1.5nH 2 O ⁇ » (XSiOi. 5 ) n +3nHY (Equation 1).
  • POSS can form from linear, cyclic, or polycyclic siloxanes that are derived from the XSiY 3 -type monomers.
  • the second class of reactions involves the manipulation of the substituents at the silicon atom without affecting the silicon-oxygen skeleton of the molecule.
  • substituents include alcohols and phenols, alkoxysilanes, chlorosilanes, epoxides, esters, fluoroalkyls, halides, isocyanates, methacrylates and acrylates, alkyl and cycloalkyl groups, nitriles, norbornenyls, olefins, phosphines, silanes, silanols, and styrenes.
  • reactive functionalities are suitable for polymerization or co-polymerization of the specific POSS derivative with other monomers.
  • non-reactive organic functionalities may be varied to influence the solubility and compatibility of POSS cages with polymers, biological systems, or surfaces.
  • the hydrolysis of trimethoxysilane may be carried out in cyclohexane— acetic acid in the presence of concentrated hydrochloric acid and leads to the octamer.
  • the hydrolytic polycondensation of trifunctional monomers of type XSiY 3 leads to cross-linked three-dimensional networks and cis-syndiotactic (ladder-type) polymers, (XSiOi.5) n .
  • the corresponding condensed polycyclosiloxanes, POSS, and their derivatives may be formed.
  • reaction rate the degree of oligomerization, and the yield of the polyhedral compounds formed under these conditions depend on several factors.
  • octa(phenylsilsesquioxane), Ph S (SiOLs) 8 is more readily formed in benzene, nitrobenzene, benzyl alcohol, pyridine, or ethylene glycol dimethyl ether at high temperatures (e.g., 10O 0 C).
  • Multifunctional POSS derivatives can be made by the condensation Of ROESi(OEt) 3 , as described above, where ROE is a reactive group.
  • This reaction produces an octa-functional POSS, R' 8 (Si0i.5) 8 .
  • Another approach involves functionalizing POSS cages that have already been formed. For example, this may be accomplished via Pt-catalyzed hydrosilylation of alkenes or alkynes with (HSiOi.s)8 and (HMe 2 SiOSiO 1- S) 8 to form octakis(hydridodimethylsiloxy) octasesquioxane cages as shown in Figure 15.
  • Another example of the synthesis of multifunctional POSS derivatives is the hydrolytic condensation of modified aminosilanes. Fasce et al., Macromolecules 32: 4757 (1999).
  • POSS units which have been functionalized with various reactive organic groups, may be incorporated into an existing polymer system through grafting or co-polymerization. POSS homopolymers can also be synthesized. The incorporation of the POSS nanocluster cages into polymeric materials may result in improvements in polymer properties, including temperature and oxidation resistance, surface hardening and reductions in flammability.
  • POSS monomers may be chemically incorporated into resins.
  • monofunctional monomers can be used.
  • di- or polyfunctional POSS monomers can be used. Incorporating a monofunctional POSS monomer can actually lower the resulting resin's cross-link density if the amount of the monofunctional POSS monomers in the commercial resin employed is held constant.
  • the POSS cages with organic functions attached to its corners have typical diameters of 1.2 to 1.5 run. Therefore, each POSS monomer occupies a substantial volume. When that POSS monomer is monosubstituted, it cannot contribute to cross-linking.
  • a 2 mol% loading of POSS in a resin might actually occupy 6 to 20 vol% of the resin, and this occupied volume contains no cross-links.
  • the macromers are designed to promote the recruitment and adhesion of osteoprogenitor cells via cell adhesive RGD epitope, retain and release exogenous BMP-2/ BMP-2/7 heterodiamer/RANKL/VEGF to simultaneously trigger new bone formation and osteoclastic remodeling of the synthetic graft with vascular ingrowth, and template the nucleation and growth of HA in situ.
  • the macromers can be further crosslinked to form stable bone grafts either prior to implantation or at the site of injection under physiological conditions.
  • the graft is also designed to degrade overtime to allow eventual replacement by newly integrated bony tissue.
  • the incorporation of the HA-binding peptide identified by the combinatorial screening approach is designed to enhance the bonding affinity of the graft with its surrounding bony tissue, as well as to facilitate the graft-templated HA-mineralization in vivo.
  • the in situ integrated HA minerals are expected to help sequester the ECM proteins (e.g. osteopontin and bone sialoprotein) secreted by osteoblasts via favorable binding of these proteins to the HA crystals. Preventing the secreted cytokines and growth factors from quickly diffusing away from synthetic scaffolds (thus maintaining their tissue-specific critical local concentrations) is an important consideration in the design of ECM mimetics.
  • the macromers are designed to degrade over time to allow its eventual replacement by new bone.
  • This is realized by the grafting of well-characterized biodegradable poly(r ⁇ c-latide) (PLA) segments to the POSS cores.
  • PPA biodegradable poly(r ⁇ c-latide)
  • the more crystalline packed poly(L-lactide) tend to degrade slowly, with degradation ranging from months to many years
  • the in vitro and in vivo hydrolysis of the amorphously packed poly(r ⁇ c-lactide) is faster (with median degradations in a few months) due to faster water uptake. It is contemplated that the in vivo degradation of the graft will coordinate with the new bone ingrowth within the time scale of the normal fracture healing.
  • a slower degradation rate and higher mechanical strength of the graft can be achieved by enhancing the L-lactide content of the PLA chains, or vise versa if the opposite effect is desired, via the stoichiometric control of the monomers during the ROP grafting.
  • Polyethylene glycol diisocyanates may be used to crosslink and stabilize the polar macromers by forming urethane linkages between the isocyanate functionality and the free carboxylates richly present in the growth factor retention domain.
  • the length of each functional domains attached to the POSS core can be independently altered during the sequential assembly of the block copolymer segments. This feature allows for the optimization of the biodegradation rate, polarity, charge, aqueous solubility and viscosity of the star-shaped macromers.
  • the cross-linker length and crosslinking density By adjusting the cross-linker length and crosslinking density, the growth factor release characteristics and the mechanical properties can be further optimized. Comparing to naturally occurring hydrogels and polysaccharides, synthetic scaffolds assembled from bottom up are characterized with better controlled physical, mechanical and biological properties.
  • the radical inhibitors in the commercially available HEMA and EGDMA were removed via distillation under reduced pressure and by passage through a 4 A molecular sieve column prior to use, respectively.
  • Polycrystalline HA powders were purchased from Alfa Aesar (Ward Hill, MA) and used as received.
  • the calcined HA powders were obtained by treating the commercial polycrystalline HA at 1100 0 C for Ih. Prior to use, the calcined powders were ground in a planetary agatar mill for 2 h and then passed through a 38 ⁇ m sieve to remove larger agglomerates. The microstructures and size distributions of these HA particles are shown in Figure 7.
  • the HA content of the FlexBone is defined as the weight percentage of the HA incorporated over the total weight of the HA, hydrogel monomer HEMA, and cross-linker ethylene glycol dimethacrylate (EGDMA) used in any given preparation, hi a typical procedure, freshly distilled HEMA was mixed with EGDMA along with ethylene glycol, water and aqueous radical initiators ammonium persulfate (480 mg/mL) and sodium metasulfite (180 mg/mL) at a volume ratio of 100:2:55:0:5:5 (formulation 1), 100:2:20:35:10:10 (formulation 2), 100:2:35:20:5:5 (formulation 3), or 100:2:60:40:5:5 (formulation 4; applied to composites containing >50% HA only).
  • EGDMA cross-linker ethylene glycol dimethacrylate
  • HA or calcined HA powder was then added to the hydrogel mixture, thoroughly mixed by using a ceramic ball to break up the large agglomerates, and allowed to polymerize in a plastic syringe barrel to afford composites with HA contents varying from 30% to 70%. The resulting rubbery material was removed from the syringe barrel.
  • Elastomeric high-mineral content composites were cut into pieces and soaked in a large volume of water overnight before freeze-drying or undergoing solvent exchange with glycerol.
  • the resulting composites are denoted as #Com/Cal-N-AP/FD, where # denotes the weight percentage of HA, Com for commercial HA, CaI for calcined HA, N for the type of hydrogel formulations (1, 2, 3 or 4), AP for as-prepared, and FD for freeze-dried.
  • # denotes the weight percentage of HA
  • Com for commercial HA
  • CaI for calcined HA
  • N for the type of hydrogel formulations (1, 2, 3 or 4
  • AP for as-prepared
  • FD freeze-dried.
  • 70Cal-4- AP represents as-prepared FlexBone with 70% calcined HA that is formed using hydrogel formulation 4
  • 40Com-3-FD represents freeze-dried FlexBone with 40% commercial polycrystalline HA that is formed using hydrogel formulation 3.
  • the composites produced by this method could be compressed or bent without fracturing, and be cut into desired shapes and sizes. While as-prepared FlexBone produced in ethylene glycol as the main solvent (formulation 1) remained highly elastic even after months of storage under ambient conditions, formulations with lower ethylene glycol-to-water ratios generated composites with reduced flexibility. The loss of water via evaporation during solidification or upon storage is likely to have contributed to the compromised elastomeric properties of FlexBone produced in low-glycerol content solvents.
  • the as-prepared composites can undergo solvent exchange with water or other viscous solvents such as glycerol, or freeze- dried (after removal of ethylene glycol by exchanging with water) to afford materials with varied strength and stiffness.
  • the residual radical initiators could be removed via solvent exchange.
  • EDS energy dispersive spectroscopy
  • the microstructures of the composites were characterized using environmental scanning electron microscopy (ESEM) on a Hitachi S-4300SEN microscope (Hitachi, Japan). The chamber pressure was kept at -35 Pa to avoid complete sample dehydration and surface charging during the observation.
  • the chemical composition was analyzed using energy dispersive spectroscopy (EDS) (Noran System SEX, Thermoelectron, USA) attached to the ESEM.
  • EDS energy dispersive spectroscopy
  • HA powder Two types were used: the commercial polycrystalline powder (Alfa Aesar, Ward Hill, MA) consisting of micrometer-sized loose aggregates of HA crystallites that are -100 run (nanocrystals) in size and HA powder calcined at 1100°C. Calcined HA powder consisted of dense particles with a bimodal size distribution at the submicrometer scale (Figure 7). Both types of HA powder were well distributed throughout the hydrogel network at all mineral contents examined, as indicated by SEM analysis. Examples of composites possessing 50% HA are shown in Figure 4 A and 4B. Excellent mineral-gel integration was maintained upon freeze drying, suggesting strong adhesion at the organic-inorganic interface. Ln addition, no detectable mineral dissociation from the composites containing up to 70% HA was observed upon storage in water at 37°C for more than one year, further supporting the strong mineral-gel integration.
  • Standard unconfined compression tests were performed to evaluate the compressive behavior of the hydrogels and the composites produced.
  • Short cylindrical samples nominally 3-6 mm in height and 4-7 mm in diameter, were cut from the bulk material using a razor blade. Full contacts of both surfaces with the rigid platens of the testing machine were examined to ensure that the cuts were parallel to each other. Testing was performed in ambient air on a high- capacity MTS servo-hydraulic mechanical testing machine (MTS Systems Corporation, Eden Prairie, MN) fitted with stiff, non-deforming platens. The samples were loaded under displacement control at a rate of ⁇ 0.015 mm/s, while the corresponding loads and displacements were continuously monitored using the in-built load cell and linear variable displacement transducer (LVDT).
  • MTS servo-hydraulic mechanical testing machine MTS Systems Corporation, Eden Prairie, MN
  • the compressive strength of the composites was dependent on the mineral content. As shown in Figure 3, the work under the compressive force-strain curve of a freeze-dried FlexBone possessing 48% commercial polycrystalline HA (48Com-3-FD) is greater than that of the sample containing 41% HA (41Com-3-FD), indicating that the higher-mineral content resulted in a stiffer, tougher, and stronger composite.
  • Rat bone marrow stromal cells BMSC were isolated from long bones of 4-week old male Charles River SD strain rats. Marrow was flushed from the femur with a syringe. After lysing red blood cells with sterile water, the marrow cells were centrifuged and resuspended in minimum essential medium (MEM) supplemented with 20% FBS, 0.2% penicillin-streptomycin and 1% L-glutamine, and passed through a sterile metal filter. Cells were expanded on tissue culture plates (10 million cells per 100-mm plate) with media changed every other day before being lifted off on day 4 for plating on FlexBone.
  • MEM minimum essential medium
  • FlexBone composites were subcutaneously implanted with and without pre-seeded BMSC in rats.
  • Thin half discs (7 mm in diameter, 1 mm in thickness) of FlexBone containing 40% calcined HA (40Cal-3-AP) or 40% commercial HA (40Com-3-AP) were sterilized in 70% ethanol, re-equilibrated with sterile water before being seeded with BMSC and used for subcutaneous implantation in rats.
  • Fifty microliters of BMSC suspension (in culture media described above) was loaded on the surface of thin disks of FlexBone to reach 5,000-cells/cm 2 or 20,000-cells/cm 2 seeding density.
  • the cell-seeded FlexBone was incubated at 37°C in humidified environment with 5% CO 2 without additional media for 6 hours to allow cell attachment to the FlexBone substrate. Additional media were then added and the cells were cultured on the substrates for 2 days before being used for implantation. Four sets of samples were used for each FlexBone composition and cell seeding treatment. Thin discs of FlexBone without pre-seeded BMSC were also used for implantation as controls.
  • Rats were anesthetized by intraperitoneal (IP) injection of ketamine/xylazine (50 mg/5 mg per kg). They were shaved and swabbed with betadine before two 0.25 inch bilateral skin incisions were made over the rib cage for insertion of the FlexBone discs with and without pre- seeded BMSC. The skin was closed with surgical staples and buprenorphine (0.02 mg/kg) was given subcutaneously. The rats were sacrificed by CO 2 inhalation and cervical dislocation at day 14 and day 28 for the retrieval of FlexBone.
  • IP intraperitoneal
  • the retrieved FlexBone was fixed in 4% paraformaldehyde (0.1 M phosphate buffer, pH 7.4) for 5 h at 4°C before being analyzed by SEM, XRD, and histology.
  • Example IV The 4% paraformaldehyde-fixed FlexBone explants of Example IV were equilibrated in cacodylic buffer overnight, then in 30% sucrose solution (pH 7.3) for 2 days before being frozen-sectioned on a Bright Cryostat (Model OTF; Bright Instrument Ltd., Huntigdon, UK). Frozen-sectioning was repeated until reaching the depth of 100-200- ⁇ m away from the surface where the BMSC were initially seeded. The 12- ⁇ m frozen sections were held on adhesive slides using frozen sectioning tape for UV cross-linking ( ⁇ 1 sec). Histological staining for ALP activity, a marker of osteogenic differentiation, was performed.
  • the explanted composites with pre-seeded BMSC were stained histochemically for alkaline phosphatase (ALP) activity, a marker for osteogenic differentiation.
  • ALP alkaline phosphatase
  • frozen sectioning was performed on the explants prior to ALP staining.
  • ALP activity indicated by red stains was detected 14 days post-implantation on the periphery of the calcined HA-containing composite pre-seeded with 5000-cells/cm 2 BMSC.
  • FlexBone composites containing 60%HA, 45%HA-15%TCP, 30%HA-30%TCP, 15%HA-45%TCP, and 60%TCP were prepared as described in Example I in syringe barrels with 3-mm inner diameters.
  • the mineral content, in weight percentage, is defined as the weight of HA/TCP divided by the combined weight of HA/TCP, HEMA and cross-linker EGDMA.
  • the as-prepared composites were equilibrated in water for 24 h, with frequent changes of fresh water, to remove residue radical initiators and unpolymerized monomers. The composites were then cut into segments of 5.5-mm in length before they were freeze-dried.
  • the composite grafts were re-hydrated in saline 30 min prior to implantation, and their final lengths are optimized by a surgical knife to match with the segmental defects before being inserted to the site of femoral defects.
  • a male Charles River. Sprague-Dawley strain rat (290 ⁇ 10 g) was anesthetized by 5% isoflurane and 2% oxygen in an induction chamber before its left hind leg was shaved bilaterally and swabbed with betadine.
  • the rat was maintained by 2% isoflurane and 2% oxygen throughout the surgery via a rodent nose mask on a heated sterile surgical area.
  • An anterior incision was made with the convexity between the base of the rat tail and the knee.
  • the shaft of the femur was exposed by blunt dissection between the vastus lateralis and the hamstring muscles.
  • a self-retaining retractor was used for exposure of the femur.
  • the soft tissue of the femur was cleaned by a bone elevator.
  • a radio-transparent polyetheretherketone (PEEK) plate with 4 pre-drilled holes was placed over the rat femur antero-laterally.
  • the design features an elevation in the middle of the plate that permits easier removal of bone and subsequent insertion of grafts.
  • a Dremel tool attached with a 1/32" drill bit (Dremel USA, Part # 660 with Collet) drilled transversely through the femur before a self-tapping cortical screw (Morris Company, Part # FF00CE250) was applied immediately after.
  • Bupivacaine (0.125% solution) was applied. The same procedure was repeated on the right femur of the rat, with or without (serving as the control) the insertion of a synthetic graft containing a different ceramic composition.
  • Buprenorphine (0.04 mg/kg SC) and Cefazolin (20 mg/kg) were administered subcutaneously as analgesics and antibiotics immediately after the surgery. The rat was then allowed to recover off the rodent ventilation machine and returned to the cage. The rats could usually regain strength to move around within 30 min to 1 h post- operation. Buprenorphine (0.02 mg/kg SC) was given twice a day for two more days and Cefazolin was given once more on the second day after the surgery. Surgical staples were removed after 14 days. We have not observed any incidents of infection using pHEMA- HA/TCP composite grafts in combination with the plate fixation technique.
  • X-ray radiographs were taken both post-operatively and biweekly thereafter to confirm the proper positioning of the graft and to follow its mineral content resorption over time until the animal is sacrificed at various time points (e.g. 4 weeks and 8 weeks post-operation) by CO 2 inhalation and cervical dislocation.
  • a pHEMA-ceramic graft containing 15% HA and 45% TCP (by weight) was snugly fit into the segmental defect and remained in place 2 weeks after the surgery despite the active movements of the rat.
  • Key features of the healing of segmental defects include the formation of a mineralized callus completely bridging the segmental defects, abundant neovascularization, and extensive resorption of bone graft.
  • Osteoclast formation was monitored by staining for tartrate-resistant acid phosphatase (TRAP), which is a marker enzyme of osteoclasts. More TRAP positive stains were detected at week 8 than at week 4. However, the overall resorption of the FlexBone grafts was limited, underscoring a preference for a biodegradable organic matrix of the graft and the exogenous supply of growth factors and cytokines to expedite the graft remodeling. EXAMPLE VIII. IN VITRO BIOACTIVITY OF GRAPHS PRE-ABSORBED WITH rhBMP-2, rmRANKL,
  • Grafts (5x5x1 mm, FlexBone 25%HA-25%TCP) were pre-absorbed with varying amounts of growth factors and cytokines to provide an exogenous supply for remodeling. Grafts loaded with growth factors rhBMP-2, rmRANKL, and rhVEGF165 were analyzed at the respective preferred doses.
  • the preferred loading dose of RANKL (10 ng/FlexBone graft) was determined by the osteoclastic differentiation of macrophage RAW264.7, induced by the RANKL released from the graft as indicated by positive TRAP stains (purple) of multinucleated cells on Day 6.
  • rh VEGFl 65 in stimulating the proliferation of human vascular endothelial cells in culture was determined to be 5 ng/graft.
  • Polymeric or polymer-HA/TCP composite grafts fabricated in a syringe barrel or plastic tubing (2-3 mm inner diameter) are cut into segments that are 5.5-mm in length, washed with water to remove residue, and freeze-dried the day before the surgery.
  • Three holes along and perpendicular to the axis of the freeze-dried graft are drilled using a Dremel tool attached with a 1/16" drill bit to facilitate the migration of bone marrow cells throughout the graft upon implantation.
  • the freeze-dried grafts are loaded with the preferred doses of BMP-2 or BMP- 2/VEGF/RANKL combination regimen in the maximal volume of aqueous buffer, as determined from the swelling ratio of the grafts, 1 h prior to implantation and kept in a humidified incubator at 37°C.
  • the grafts without growth factor loading and the pHEMA control are equilibrated in saline in a similar fashion.
  • Grafts of FlexBone (25%HA-25%TCP) absorbed with 40-ng rhBMP-2/7, 10-ng rmRANKL+5-ng rhVEGF165, or 40-ng rhBMP-2/7+ 10-ng rmRANKL+5-ng rhVEGF165 were press-fitted in 5-mm rat femoral defect sites, along with autograft control, pHEMA control and FlexBone control without growth factors.
  • Radiography follow-ups showed only ⁇ 10% of the grafts were dislocated 2 weeks post-op, suggesting that the pre-drilled holes did not compromise the structural stability of the grafts.
  • Substantial callus formation was observed by week 2 with the FlexBone graft containing a combination of 40-ng rhBMP-2/7+ 10-ng rmRANKL+5-ng rh VEGFl 65, suggesting that these exogenous growth factors and cytokines accelerate graft healing.
  • Trithiocarbonate and dithioester chain transfer agents were synthesized as provided in Mitsukami et al., Macromolecules 2001, 34, 2248-2256 and Convertine et al., Macromolecules 2006, 39, 1724-1730.
  • the attachment of the trithiocarbonate chain transfer agent CTA-I, via the active acyl chloride intermediate, to the PLA termini of macromer 2 was accomplished in 92% yield ( Figure 10). Briefly, oxalyl chloride (1.455 g, 11.46 mmol) was reacted with CTA-I (0.4662 g, 2.078 mmol) under N 2 for 2 h at room temperature and then 3 h at 55°C.
  • the efficiency for the macromer CTA to initiate RAFT polymerization was first investigated by grafting 2-hydroxyethyl methacrylate (HEMA) to each arm of the macromer.
  • HEMA 2-hydroxyethyl methacrylate
  • PEG poly(ethylene glycol)
  • 1 and 5 kD poly(ethylene glycol)
  • isocyanate on both ends by reacting PEG with isophorone diisocyanate in 1,1,1- trichloroethane at elevated temperature in the presence of catalytic amount of dibutyltin dilaurate ( Figure 22).
  • One obtains different graft porosity and strength by using small molecule diisocyanates or PEG-diisocyanates with varying molecular weights (e.g. 1-5 kD) and crosslinking density (1, 2, 4 eq. PEG-diisocyanate per polymer arm, or 8, 16, 32 eq. PEG- diisocyanate per macromer).
  • dichloromethane solution of macromers O.lg/ml
  • hexamethylene diisocyanate or PEG-diisocyanate (1 eq.) at room temperature for 15 min before being cast into molds to form films or bulk materials of desired shapes.
  • the residue volatile components were removed in a vacuum oven at 7O 0 C.
  • GIy-MA Two methacrylamides containing azido side chain (for click chemistry) and glycine side chain (for retaining growth factors) were prepared (Fig. 18). One functionalizes them to produce the corresponding macromer as provided in Examples 10 and 11.
  • the synthesis of GIy-MA was achieved by coupling the N-terminus of glycine with methacryloyl chloride.
  • 3-Azidopropan-l-ol Sodium azide (3.92 g, 60.0 mmol) and 3-Bromo-l-propanol (5.00 g, 36.0 mmol) were dissolved in a mixture of acetone (60 mL) and water (12 mL), and refluxed at 75 0 C for 1O h. After removing acetone under vacuum, 40 mL of water was added. The solution was extracted with 50 mL of ethyl ether 3 times. The ether phase was dried by anhydrous MgSO 4 and the solvent was removed by rotary evaporation, resulting in 3.00 g colorless oil (yield ⁇ 83%).
  • 3-Azidopropyl methacrylate (MA-C3-N3): 3-Azidopropan-l-ol (1.010 g, 100.0 mmol) and triethylamine (1.220 g, 120.0 mmol) were mixed with 10 mL dichloromethane in an ice bath. Methacryloyl chloride (1.144 g, 110.0 mmol) was slowly added by a syringe in 30 min. The reaction was allowed to proceed in ice bath for 1 h before being warmed to room temperature and continued for another 2 h. After removing the insoluble salt by filtration, the filtrate was washed with 50 mL saturated NaHCO 3 aqueous solution 3 times.
  • the 6-carbon linker on the N-terminus of the HA-12 is designed to minimize the conformational perturbation of the peptide upon its covalent attachment to the macromer, ensuring the maintenance of its HA- nucleating capacity.
  • methacrylamido group was attached to the N-terminus of the peptides, via the reaction of C6-HA12 and GRGDS with methacryloyl chloride in THF-H 2 O (pH 8) to form MA-C6-HA12 and MA-GRGDS, respectively.
  • the methacrylamido and alkynyl groups are introduced to allow the covalent coupling of these peptides to the star-shaped macromers.
  • Polyhedral oligomeric silsesquioxane (POSS) nanoparticles are designed as the structural and mechanical anchors for grafting multiple functional polymer domains to form the star-shaped macromers.
  • POSS polyhedral oligomeric silsesquioxane
  • an HA-nucleation domain containing the HA-binding peptide (HA- 12), a negatively charged polymethacrylamide growth factor retention domain and a cell adhesion domain containing the integrin-binding Arg-Gly-Asp (RGD) epitope are sequentially grafted via RAFT polymerization.
  • the R and Z groups depicted in Figure 19 are the fragments of the chain transfer agent (CTA) attached to the macromer for initiating the RAFT, he POSS nanoparticle cores do not affect the radio-transparency of the hybrid polymer grafts, allowing for noninvasive tracking of the osteointegration of the polymer grafts by X-ray radiography.
  • CTA chain transfer agent
  • RAFT To initiate the RAFT, one covalently attaches previously prepared chain transfer agents CTA-I and CTA-2 to the terminal hydroxyls of macromer 2 via esterification under the activation of 1,3-dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridine (DMAP) (Fig. 21).
  • DCC 1,3-dicyclohexylcarbodiimide
  • DMAP 4-(dimethylamino)pyridine
  • the resulting macromer CTAs can generate benzyl or tertiary carbon radicals along the cleavage site (Fig. 21, top right), initiating subsequent RAFT grafting of polar polymer segments to the R fragment, capping the polymers with the Z fragment.
  • Fig. 21 An alternative strategy towards the synthesis of functional macromer 5' containing similar HA-nucleating domains, growth factor retention domains and cell adhesive domains is provided in Fig. 21 (route 2). Instead of directly grafting the highly polar peptide-containing methacrylamides to macromer CTAs, one grafts a less polar azido-containing methacrylamide MA-C3-N3. RAFT polymerization of less polar components results in higher overall yields and narrower molecule weight distributions.
  • Formation of the stable triazoles between azides and terminal alkynes may be done in the presence of other functional groups in aqueous or polar aprotic media.
  • Polymers with azido or alkyne pendant side chains can both be prepared as "clickable” polymers.
  • the use of acetylene-containing monomers in radical polymerizations can be complicated by the undesired addition of the propagating radicals to the acetylene groups. Therefore, one avoids this complication by preparing "clickable" macromers containing the azido residues (macromer-N3) instead.
  • the radical inhibitors in the commercial HEMA and ethylene glycol dimethacrylate (EGDMA) from Aldrich (Milwaukee, WI) were removed via distillation under reduced pressure and by passing through a 4 A molecular sieve column prior to use, respectively.
  • Polycrystalline commercial HA powders (designated as ComHA) were purchased from Alfa Aesar (Ward Hill, MA) and used as received.
  • the calcined HA powders (designated as CaIHA) were obtained by treating ComHA at 1100 0 C for 1 h. Prior to use, the CaIHA powders were ground in a planetary agate mill for 2 h and then passed through a 38 ⁇ m sieve to remove larger agglomerates.
  • HA particles The microstructures and size distributions of these HA particles are shown in Figure 26.
  • Cell culture media and supplements were purchased from Invitrogen (Carlsbad, CA) and the fetal bovine serum was purchased from HyClone (Logan, UT). All reagents for histochemistry were purchased from Sigma (St Louis, MO).
  • the HA content of the FlexBone is defined as the weight percentage of the HA incorporated over the total weight of the HA, monomer HEMA, and crosslinker EGDMA used in any given preparation.
  • EGDMA ethylene glycol
  • aqueous radical initiators ammonium persulfate (1-1, 480 mg/mL) and sodium metasulfite (1-2, 180 mg/mL) at a volume ratio of HEMA:EGDMA:EG:I-l:I-2/100:2:35:20:5:5 (formulation 1).
  • ComHA or CaIHA powder was then added to the hydrogel mixture, thoroughly mixed by using a ceramic ball to break up the large agglomerates, and allowed to polymerize in a disposable syringe barrel or rigid PMMA tubing of a 7.0-mm or 4.7-mm inner diameter to afford composites with HA contents varying from 37 to 50%.
  • the resulting elastic material was either used as it was (as-prepared), thoroughly exchanged with a large volume of water (fully hydrated), or freeze-dried.
  • ComHA-N-# or CaIHA- N-#, where N stands for the type of hydrogel formulation and # denotes the weight percentage of HA content.
  • ComHA-1-50 represents FlexBone composite containing 50% commercial HA that is formed using crosslinking formulation 1.
  • Unmineralized pHEMA control was prepared using formulation 1 in the absence of HA particles.
  • the microstructures of the composites were characterized using environmental scanning electron microscopy (ESEM) on a Hitachi S-4300 SEN microscope (Hitachi, Japan). The chamber pressure was kept at approximately 35 Pa to avoid complete sample dehydration and surface charging during the observation.
  • the chemical composition was analyzed using energy dispersive spectroscopy (EDS) (Noran System SEX, Thermoelectron, USA) attached to the ESEM.
  • EDS energy dispersive spectroscopy
  • At least five specimens were tested for each sample.
  • cylindrical specimens with a diameter of 4.7 mm were transversely cut into 5.0-mm long cylinders using a custom-machined parallel cutter with adjustable spacing. Any visible roughness of the top and bottom surfaces of each specimen was reduced by sandpaper. An L-square was used to make sure that these surfaces were parallel prior to testing, and the final dimensions of each specimen were measured by a digital caliper.
  • cylindrical specimens with the dimension of 7 mm x 6 mm (diameter x height) were used.
  • the instrument has an 18-N load cell, a force resolution of 10 ⁇ N and a displacement resolution of 1.0 nm.
  • the as-prepared samples were compressed in a force-controlled mode in ambient air, ramping from 0.01 to 18.0 N at a rate of 3.0 N/min then back to 0.01 N at the same rate.
  • Thin half discs (7 mm in diameter, 1 mm in thickness) of FlexBone containing 40% ComHA (ComHA-1-40) were sterilized in 70% ethanol, re-equilibrated with sterile water before being seeded with BMSC and used for subcutaneous implantation in rats.
  • Fifty microliters of BMSC suspension (in culture media described above) was loaded on the surface of thin disks of FlexBone to reach 5000-cells/cm 2 or 20,000-cells/cm 2 seeding density.
  • the cell-seeded FlexBone were incubated at 37°C in humidified environment with 5% CO 2 without additional media for 6 h to allow cell attachment to the FlexBone substrate.
  • the rats were sacrificed by CO 2 inhalation and cervical dislocation at day 14 and day 28 for the retrieval of FlexBone. After removing the fibrous tissue encapsulation, the retrieved FlexBone was fixed in 4% paraformaldehyde (0.1 M phosphate buffer, pH 7.4) for 5 h at 4°C before being analyzed by SEM, XRD, and histology.
  • the crystalline phases of the mineral in the FlexBone composites before and after subcutaneous implantation in rats were evaluated by XRD with a Siemens D500 instrument using Cu Ka radiation. Phases were identified by matching the diffraction peaks to the JCPDS files.
  • FlexBone composites with varying mineral contents were prepared by crosslinking HEMA with 2% EGDMA in the presence of either porous aggregates of HA nanocrystals (ComHA) or compact micrometer-sized calcined HA (CaIHA) particles (Fig. 26) using ethylene glycol as a solvent.
  • ComHA porous aggregates of HA nanocrystals
  • CaIHA compact micrometer-sized calcined HA particles
  • the peak contact stresses in natural human joints during light to moderate activity typically range from 0.5-6 MPa by most in vitro measurements as provided for in Ahmed et al., Journal of Biomechanical Engineering 105, 216-225 (1983); Brown et al., Journal of Biomechanics 16, 373-384 (1983); Whalen et al., Journal of Biomechanics 21, 825- 837 (1988) and Brand et al., Iowa Orthopedic Journal 25, 82-94 (2005), all of which are hereby incorporated by reference, and up to 18 MPa by some in vivo measurements as provided for in Hodge et al, Proceedings of the National Academy of Sciences USA 83, 2879-2883 (1986) and Hodge et al., Journal of Bone and Joint Surgery 77,1378-1386 (1989), both of which are incorporated by reference. Overall, our data suggest that as-prepared FlexBone exhibit excellent shape recovery under repetitive, physiologically relevant compressive stress despite their high (37-50%) mineral contents.
  • the as-prepared composites can undergo solvent exchange with water to give fully hydrated FlexBone.
  • the residue sulfur-containing radical initiators trapped in the as-prepared composites could be removed during the wash with water as indicated by the disappearance of the S signal detected from the energy dispersive spectroscopy (EDS) performed on the cross- section of the composite upon equilibration with water as shown in Figure 27B.
  • EDS energy dispersive spectroscopy
  • the compressive behavior of fully hydrated FlexBone was examined at body temperature in water using a DMA equipped with a submersion compression fixture.
  • Figure 27C mineral content-dependent and mineral microstructure-dependent compressive behavior similar to those exhibited by as-prepared FlexBone was observed with fully hydrated FlexBone.
  • the explanted composites with preseeded BMSC were stained histochemically for alkaline phosphatase (ALP) activity, a marker for osteogenic differentiation as disclosed in Vanhoof et al. Critical Reviews in Clinical Laboratory Science 31, 197-293 (1994), hereby incorporated by reference.
  • ALP alkaline phosphatase
  • frozen sectioning was performed on the explants prior to ALP staining.
  • ALP activity (indicated by red stains) was detected 14 days post-implantation on the periphery of the ComHA- 1-40 preseeded with 5000-cells/cm 2 BMSC. More extensive ALP activity was also detected 28 days after the implantation on FlexBone pre-seeded with 20,000-cells/ cm 2 BMSC.
  • Subcutaneous implantation of ComHA- 1-40 preseeded with BMSC in rats showed that the osteoconductive composite provided a cytocompatible environment to support the attachment, penetration, and osteogenic differentiation of BMSC in vivo.
  • An ideal synthetic bone graft is designed to fill an area of defect to provide immediate structural stabilization and to expedite the healing and repair of the skeletal lesion.
  • the synthetic grafts can be eventually remodeled and replaced by newly synthesized bone. From this perspective, biodegradability and osteoinductivity of the synthetic bone grafts are just as important as their osteoconductivity, mechanical strength, and material handling characteristics (e.g. elasticity facilitating surgical insertion).
  • Future improvements include engineering the biodegradability of the organic matrix, enhancing the in vivo dissolution rate of the osteoconductive mineral component to the mineral phase e.g. by introducing the more soluble ⁇ -tricalcium phosphate, ⁇ - TCP as provided for in Kwon et al., Journal of the American Ceramic Society 85, 3129-3131 (2002), hereby incorporated by reference, while locally retaining and releasing osteoinductive growth factors and cytokines on and from the synthetic scaffold.
  • HEMA 2-hydroxyethyl methacrylate
  • EGDMA ethylene glycol dimethacrylate
  • TCP ⁇ -tricalcium phosphate powders
  • FBS fetal bovine serum
  • rhBMP-2/7 heterodimer and rmRANKL recombinant proteins rhBMP-2/7 heterodimer and rmRANKL were purchased from R&D Systems (Minneapolis, MN) and reconstructed according to vendor instructions prior to use.
  • Tetracycline hydrochloride (TCH, >95%) and all reagents for histochemistry were purchased from Sigma (St. Louis, MO).
  • FlexBone composites containing between 0 and 5.0 wt% TCH were prepared using a protocol as described in Example XVIII. In a typical procedure, 0-5.0 wt% TCH was dissolved in the mixture of freshly distilled monomer HEMA, 2% cross-linker EGDMA and viscous solvent ethylene glycol under bath-sonication, before 25 wt% HA, 25 wt% TCP, and the aqueous radical initiators ammonium persulfate and sodium metasulfite were added and thoroughly mixed (Table I).
  • the pasty mixture was immediately drawn into a rigid acrylic tubing (Um ' ted States Plastic Corp., pre-washed with ethanol to remove radical inhibitors and air-dried prior to use) of an inner diameter of 1/8" (3.2 mm) or 3/16" (4.8 mm), and allowed to solidify at room temperature overnight.
  • the resulting elastic material was either used as it was for antibiotic release kinetics study and E. coli inhibition assay, or thoroughly exchanged with a large volume of water for 24 h (to remove ethylene glycol and residue unpolymerized monomer and radical initiators) for subsequent mechanical testing and cell culture study.
  • TCH Release kinetics from FlexBone vs. from pHEMA has strong optical absorptions at the UV- Vis region, enabling the characterization of its release kinetics by spectroscopy as disclosed in He et ah, Journal of Macromolecular Science B 45, 515-524 (2006) and Kenawy et al., Journal of Controlled Release 81, 57-64 (2002), both of which are incorporated by reference.
  • the release of TCH from FlexBone vs. pHEMA hydrogel in water as a function of time and the initial TCH incorporation was monitored over 1 week at 357.9 run.
  • the release kinetics was determined by quantifying the TCH released into water at various time points.
  • a standard absorption-TCH concentration curve was generated by preparing and measuring the absorption of TCH standards (100 mM, 1.0 mM, 100 ⁇ M, 50.0 ⁇ M, 25.0 ⁇ M, 10.0 ⁇ M, 5.0 ⁇ M, 2.0 ⁇ M, 1.0 ⁇ M, and 0.5 ⁇ M) at 357.9 nm. Percentage of TCH release from FlexBone or pHEMA was plotted over time for each composition examined.
  • the antibiotic activity of the TCH released from FlexBone or Phema was evaluated by its ability to inhibit E. coli culture.
  • Warm LB (25 g/L)-Agar (15 g/L) solution was poured into P-150 cell culture dishes (35 mL/plate) and cooled to room temperature.
  • EWC Equilibrium water content
  • EWC [(hydrated weight - dry weight) / dry weight] * 100%.
  • the average EWCs for FlexBone and pHEMA were determined as 37.99 ⁇ 0.64% and 50.16 ⁇ 0.69%, respectively.
  • Recombinant protein rhBMP-2/7 was reconstructed according to the manufacturer's instruction, and the protein solution was applied to freeze-dried FlexBone in the pre-determined maximal aqueous loading volume (V max ) to yield the final loading dose of 20 ng/graft.
  • Recombinant protein rmRANKL was loaded in a similar fashion to both freeze-dried FlexBone and freeze-dried pHEMA control to reach a 10 ng/graft final loading dose.
  • C2C12 cells were seeded at 5,000/cm in a 24-well plate in DMEM (0.5 mL/well) supplemented with 10% FBS and 1% Pen-Strep, and allowed to attach overnight.
  • DMEM 0.5 mL/well
  • pen-Strep 10% FBS and 1% Pen-Strep
  • rhBMP-2/7 was supplemented directly in the low mitogen media (40-ng/mL) without a FlexBone carrier on day one.
  • Cells were fixed on day 3 by 4% paraformaldehyde (in PBS, pH 7.4), and stained for alkaline phosphatase (ALP), a marker of osteogenic differentiation, in 0.1 M Tris acid maleate buffer (pH 8.4) containing 1.5 mM naphthol-As-Mx phosphate disodium salt, 0.1% Fast Red and 2.7% DMF (v/v) for 30 min as provided for in Drissi et al., Cancer Research 59, 3705-3711 (1999), incorporated herein by reference.
  • ALP alkaline phosphatase
  • Osteoclastic differentiation of murine macrophage RAW264.7 cells induced by the rmRANKL released from FlexBone The bioactivity of the exogenous rmRANKL released from FlexBone is evaluated by its ability to induce osteoclastic differentiation of murine macrophage RAW264.7 cells six days after placing the FlexBone graft pre-loaded with rnRANKL in the
  • RAW264.7 culture RAW264.7 cells were seeded at 10,000/cm in a 24-well plate in alpha- MEM (0.5 mL/well) supplemented with 10% FBS and 1% Pen-Strep, and allowed to attach overnight.
  • alpha- MEM 0.5 mL/well
  • Pen-Strep Pen-Strep
  • 10 ng rmRANKL was supplemented directly in the culture media without a graft carrier every two days.
  • the TCP-containing FlexBone was still able to withstand >10 consecutive moderate compressive loading/unloading cycles without fracturing when as much as half of the nanometer-sized HA was replaced by the more compact TCP.
  • the maximal compressive stress applied >1 MPa for as-prepared sample and 0.6 MPa for hydrated sample
  • the TCP-containing FlexBone was able to recover from up to 30% repetitive compressive strains, suggesting that it had maintained the desired elastomeric and fracture-resistant surgical handling characteristics.
  • a piece of fully hydrated FlexBone containing 25 wt% HA-25 wt% TCP was readily press-fitted into a 5-mm segmental defect in rat femur.
  • Tetracyclines are broad-spectrum antibiotics that are also known for their non-antimicrobial capacity to reduce pathological bone resorption via MMP inhibition as disclosed in Greenwald et al, Bone 22, 33-38 (1998); Williams et al, Inhibition of Matrix Metalloproteinases: Therapeutic Applications, 191-200 (1999) and Holmes et al., Bone 35, 471-478 (2004), all of which are incorporated herein by reference, and promote bone formation as disclosed in Golub et al., Research Communications in Chemical Pathology and Pharmacology 68, 27-40 (1990); Williams et al., Bone 19, 637-644 (1996); Sasaki et al, Calcified Tissue International 50, 411-419 (1992); Sasaki et al, Anatomical
  • TCH released from FlexBone was examined by its ability to inhibit E. coli culture. As shown in Figure 32B, the TCH released from FlexBone inhibited E. coli culture as indicated by the formation of the clear zones surrounding the grafts placed over the surface of the E. coli agar plate by 8 hours. The clear zones were sustained throughout the two-day-old bacterial culture.
  • BMP-2/7 heterodimer known for its more potent osteogenicity than either BMP-2 or BMP-7 homodimer as provided for in Zhu et al., Journal of Bone and Mineral Research 19, 2021-2032 (2004) and Laflamme et al., Biomedical Materials 3 (2008), both of which are hereby incorporated by reference, is chosen as an osteogenic component to promote the osteointegration of FlexBone upon implantation to a site of skeletal defect.
  • rmRANKL Sustained release of rmRANKL from FlexBone induces osteoclast differentiation of RAW264.7 cells in culture.
  • RANKL regulates osteoclastic bone resorption during skeletal repair and bone graft remodeling as disclosed in Ito et ah, Nature Medicine 11, 291-297 (2005) and Kon et al., Journal of Bone and Mineral Research 16, 1004-1014 (2001), both of which are hereby incorporated by reference.
  • Osteoclasts are hematopoietically derived, multinucleated cells that arise from the monocyte/macrophage lineage as provided fo rin Ash et al, Nature 283, 669-670 (1980), incorporated herein by reference.
  • RANKL which is expressed on both stromal cells and osteoblasts, plays an essential role in the regulation of osteoclast differentiation as provided for in Hsu et al, Proceedings of the National Academy of Sciences USA 96, 3540-3545 (1999); Yasuda et al, Proceedings of the National Academy of Sciences USA 95, 3597-3602 (1998) and Lacey et al, Cell 93, 165-176 (1998), all of which are incorporated by reference. Soluble recombinant form of RANKL was found sufficient in the induction of osteoclast differentiation from macrophage in in vitro cultures.
  • RANKL-induced osteoclast differentiation of murine macrophage cells RAW264.7 as a cell culture model for this investigation.
  • RAW 264.7 cells are known to express high levels of RANK mRNA as provided for in Hsu et al, Proceedings of the National Academy of Sciences USA 96, 3540-3545 (1999) and can be differentiated into osteoclasts upon the induction of RANKL.
  • Bone is a natural organic- inorganic structural composite.
  • the mineral component of bone (its content, its structural integration with the organic matrices, and its affinity for a wide range of matrix proteins and soluble factors) plays an important role in defining the structural, mechanical and biochemical properties of the calcified tissue as disclosed in Follet et al, Bone 34, 783-789 (2004); Tong et al, Calcified Tissue International 72, 592-598 (2003); Gilbert et al, Journal of Biological Chemistry 275, 16213-16218 (2000) and Stubbs et al., Journal of Bone and Mineral Research 12, 1210-1222, all of which are hereby incorporated by reference.
  • FlexBone is a structural composite consisting of a high content of osteoconductive HA/TCP minerals (50 wt%) that are well dispersed and integrated within an elastomeric crosslinked pHEMA hydrogel network.
  • the minimal loading doses of these biomolecules determined in the cell culture study also provide a rational starting point for the subsequent evaluation of the in vivo performance of FlexBone with and without exogenous growth factors using a rat femoral segmental defect model.
  • a wide range of therapeutic agents and signaling molecules can be integrated with FlexBone. This provides an exciting opportunity to utilize the elastic osteoconductive composite bone graft to augment the biochemical microenvironment of hard-to-heal bony defects resulting from aging, cancer, trauma or metabolic diseases, contributing to the more effective surgical treatment of these debilitating conditions.

Abstract

L'invention a pour objet des matériaux composites qui contiennent une matrice polymère et des agrégats, et dans certains modes de réalisation, des procédés de fabrication, et des procédés d'utilisation de ces matériaux. De préférence, les agrégats sont des agrégats de phosphate de calcium. De préférence, le matériau est résistant à la fracture. Dans d'autres modes de réalisation, les matériaux sont utilisés dans des protocoles chirurgicaux de remplacement osseux. Dans d'autres modes de réalisation, les matériaux contiennent des silsesquioxanes polyédriques et/ou des segments biodégradables. Dans d'autres modes de réalisation, la matrice polymère comprend des biomolécules.
PCT/US2008/009253 2007-08-03 2008-07-31 Compositions polymères pour des applications biomédicales et dans le domaine des matériaux WO2009025719A1 (fr)

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